Fix: pathing of managerEntries containing long paths with hidden folders

[ndelangen]

Issue: #20427
Issue: #20513

What I did

• Ensured that when writing files to the cache wrapping managerEntries, to flatten the directory structure, removing special characters such as @ and . which might have meaning in the file-system.
• Strip away some redundant path info
• Ensure each entry is unique by adding the index into the path

[ndelangen]

@Jarvis1010 @fmal If you'd care to take a look, perhaps review? I think this will resolve both issues.

[Jarvis1010]

Looks like a great fix from what I can see

[fmal]

@ndelangen i have unplugged @storybook/builder-manager and applied your changes.

These are the sanitized paths after changes:

And index.html from manager bundle:

So it indeed resolved the issue! Now I can successfully serve the production build.

Thanks so much 👍

[fmal]

@IanVS I can confirm this resolves the issue, so would appreciate merge and pre-release 😃 Thanks guys 👍

[ndelangen]

@shilman self merging, can you do a release, please?