Fix bug where mutations menu would show wrong workflow

[MetRonnie]

Fixes a bug where navigating between running workflows and clicking on the workflow hamburger button would bring up the menu for the previous workflow. Closes #1006.

Note: It is not possible to write an e2e test for the bugfix while we only have one workflow in the mock/demo mode, so reviewers should test manually. You may want to review commit-by-commit.

This also changes the way the mutations menu is handled while the set of mutations is still loading. Instead of waiting until the mutations have loaded before allowing the user to open the menu, it now opens the menu and displays a skeleton loader until the mutations have loaded.

In practice the time it takes to load the mutations is small but for testing purposes you can manually delay the loading by e.g. 15s by applying this patch:

diff --git a/src/services/workflow.service.js b/src/services/workflow.service.js
index d2a438c..7c923e9 100644
--- a/src/services/workflow.service.js
+++ b/src/services/workflow.service.js
@@ -118,6 +118,7 @@ class WorkflowService {
   async loadMutations () {
     // TODO: this assumes all workflows use the same schema which is and
     //       isn't necessarily true, not quite sure, come back to this later.
+    await new Promise(resolve => { setTimeout(resolve, 15e3) })
     const response = await this.apolloClient.query({
       query: getIntrospectionQuery(),
       fetchPolicy: 'no-cache'

Also adds test for:

• Fix mutations-load race condition #979
• aotf: fix mutations in workflow toolbar #999

Requirements check-list

• I have read CONTRIBUTING.md and added my name as a Code Contributor.
• Contains logically grouped changes (else tidy your branch by rebase).
• Does not contain off-topic changes (use other PRs for other changes).
• Appropriate tests are included (unit and/or functional).
• Changelog entry included.
• No documentation update required.

[MetRonnie]

The diff is not so helpful for the remainder of this file; you may want to tick "Hide whitespace"

[MetRonnie]

This results in less faff when importing typedefs separately from the proper imports (like how we use if TYPE_CHECKING: in Python)

[MetRonnie]

(This is just to allow VSCode intellisense to work)

[MetRonnie]

Remember that empty arrays are truthy in JavaScript! Always use .length for testing conventional truthiness otherwise you're just testing that it is not undefined

[AaronDCole]

Works great Ronnie! Tested running three concurrent workflows with five old workflows, no issues that I can see.

[datamel]

Checked out and tested manually, including the auth changes via test user account. Working smoothly for me.