fix: fixed page data DB call getting called twice (appsmithorg#36247)

## Description
After perf updates made in PR
https://github.com/appsmithorg/appsmith/pull/36118/files, Page data DB
fetch call was getting triggered twice, one for PAGES_SPAN and one for
ACTIONS_SPAN. With this PR, we have replaced that a single Mono which is
being cached.

More details:
https://theappsmith.slack.com/archives/C024GUDM0LT/p1725960912325389


Fixes #`Issue Number`  
_or_  
Fixes appsmithorg#36243
> [!WARNING]  
> _If no issue exists, please create an issue first, and check with the
maintainers if the issue is valid._

## Automation

/ok-to-test tags="@tag.Sanity"

### 🔍 Cypress test results
<!-- This is an auto-generated comment: Cypress test results  -->
> [!TIP]
> 🟢 🟢 🟢 All cypress tests have passed! 🎉 🎉 🎉
> Workflow run:
<https://github.com/appsmithorg/appsmith/actions/runs/10808901838>
> Commit: d36df4c
> <a
href="https://internal.appsmith.com/app/cypress-dashboard/rundetails-65890b3c81d7400d08fa9ee5?branch=master&workflowId=10808901838&attempt=1"
target="_blank">Cypress dashboard</a>.
> Tags: `@tag.Sanity`
> Spec:
> <hr>Wed, 11 Sep 2024 09:49:39 UTC
<!-- end of auto-generated comment: Cypress test results  -->


## Communication
Should the DevRel and Marketing teams inform users about this change?
- [ ] Yes
- [x] No


<!-- This is an auto-generated comment: release notes by coderabbit.ai
-->
## Summary by CodeRabbit


- **Performance Improvements**
- Enhanced the page loading process by implementing a caching mechanism
for retrieving branched page data, potentially reducing database calls
and improving overall application performance.
- Streamlined the retrieval logic for branched pages, ensuring
consistent execution regardless of the base page ID state.

<!-- end of auto-generated comment: release notes by coderabbit.ai -->

---------

Co-authored-by: “sneha122” <“[email protected]”>

app/server/appsmith-server/src/main/java/com/appsmith/server/services/ce/ConsolidatedAPIServiceCEImpl.java

@@ -201,6 +201,9 @@ public Mono<ConsolidatedAPIResponseDTO> getConsolidatedInfoForPageLoad(
         boolean isViewMode = ApplicationMode.PUBLISHED.equals(mode);
 
         /* Fetch default application id if not provided */
+        if (isBlank(basePageId)) {
+            return Mono.when(fetches).thenReturn(consolidatedAPIResponseDTO);
+        }
         Mono<Application> branchedApplicationMonoCached;
         Mono<String> baseApplicationIdMono = Mono.just("");
         if (isViewMode) {
@@ -215,36 +218,29 @@ public Mono<ConsolidatedAPIResponseDTO> getConsolidatedInfoForPageLoad(
                 .tap(Micrometer.observation(observationRegistry))
                 .cache();
 
-        Mono<NewPage> branchedPageMonoCached = Mono.empty();
-        if (!isBlank(basePageId)) {
-            branchedPageMonoCached = newPageService
-                    .findByBranchNameAndBasePageIdAndApplicationMode(branchName, basePageId, mode)
-                    .cache();
-        }
+        Mono<NewPage> branchedPageMonoCached = newPageService
+                .findByBranchNameAndBasePageIdAndApplicationMode(branchName, basePageId, mode)
+                .cache();
 
         branchedApplicationMonoCached = baseApplicationIdMono.flatMap(cachedBaseApplicationId -> {
             if (!StringUtils.hasText(cachedBaseApplicationId)) {
                 // Handle empty or null baseApplicationId
-                return newPageService
-                        .findByBranchNameAndBasePageIdAndApplicationMode(branchName, basePageId, mode)
-                        .flatMap(branchedPage ->
-                                // Use the application ID to find the complete application details.
-                                applicationService
-                                        .findByBranchedApplicationIdAndApplicationMode(
-                                                branchedPage.getApplicationId(), mode)
-                                        .flatMap(application -> {
-                                            if (isViewMode) {
-                                                // Update the cache with the new application’s base ID for future
-                                                // queries.
-                                                return cacheableRepositoryHelper
-                                                        .fetchBaseApplicationId(basePageId, application.getBaseId())
-                                                        .thenReturn(application)
-                                                        .name(getQualifiedSpanName(
-                                                                APPLICATION_ID_UPDATE_REDIS_SPAN, mode))
-                                                        .tap(Micrometer.observation(observationRegistry));
-                                            }
-                                            return Mono.just(application);
-                                        }));
+                return branchedPageMonoCached.flatMap(branchedPage ->
+                        // Use the application ID to find the complete application details.
+                        applicationService
+                                .findByBranchedApplicationIdAndApplicationMode(branchedPage.getApplicationId(), mode)
+                                .flatMap(application -> {
+                                    if (isViewMode) {
+                                        // Update the cache with the new application’s base ID for future
+                                        // queries.
+                                        return cacheableRepositoryHelper
+                                                .fetchBaseApplicationId(basePageId, application.getBaseId())
+                                                .thenReturn(application)
+                                                .name(getQualifiedSpanName(APPLICATION_ID_UPDATE_REDIS_SPAN, mode))
+                                                .tap(Micrometer.observation(observationRegistry));
+                                    }
+                                    return Mono.just(application);
+                                }));
             } else {
                 // Handle non-empty baseApplicationId
                 return applicationService.findByBaseIdBranchNameAndApplicationMode(