feat: implement new mechanisms for generating and managing attachment…

… thumbnails (#6454)

#### What type of PR is this?
/kind feature
/area core
/milestone 2.19.x

#### What this PR does / why we need it:
实现了图片类型的附件缩略图生成和管理的新机制

实现依据 RFC：halo-dev/rfcs#24

使用缩略图前需要配置 externalUrl 才能生成

**How to test it?**
1. 测试本地缩略图的文件是否正确，每个图片对应到相应 size 的目录如 thumbnails/w400 应该是一对一
2. 每个图片生成缩略图的只会在 `http://localhost:8090/apis/storage.halo.run/v1alpha1/thumbnails` 中存在一份记录
3. 测试删除附件会删除对应的缩略图文件和 [thumbnails](http://localhost:8090/apis/storage.halo.run/v1alpha1/thumbnails) 
记录
4. 修改 externalUrl 以上功能均不会受到影响

#### Which issue(s) this PR fixes:
Fixes #2387 

#### Does this PR introduce a user-facing change?
```release-note
附件图片支持生成多尺寸图片，文章支持响应式图片。
```

api-docs/openapi/v3_0/apis_console.api_v1alpha1.json

@@ -3393,6 +3393,12 @@
           "permalink": {
             "type": "string",
             "description": "Permalink of attachment.\nIf it is in local storage, the public URL will be set.\nIf it is in s3 storage, the Object URL will be set.\n"
+          },
+          "thumbnails": {
+            "type": "object",
+            "additionalProperties": {
+              "type": "string"
+            }
           }
         }
       },