Docs: Fix issue with referencing non-story files with names similar or equal to docs files

[tmeasday]

Closes #20958

A MDX file can reference a component or other non-story file with the same prefix as an MDX file, which leads to a matching entry in the cache but that entry will not have been processed yet. That's OK, we just assume that import is not a story file (rather than throwing).

• Match file names a little more strictly
• Just continue if we find a matching non-story entry (like we never found it).

How to test

See test cases and example from issue.

Checklist

• Make sure your changes are tested (stories and/or unit, integration, or end-to-end tests)
• Make sure to add/update documentation regarding your changes
• If you are deprecating/removing a feature, make sure to update
  MIGRATION.MD

Maintainers

• If this PR should be tested against many or all sandboxes,
  make sure to add the ci:merged or ci:daily GH label to it.
• Make sure this PR contains one of the labels below.

["cleanup", "BREAKING CHANGE", "feature request", "bug", "documentation", "maintenance", "dependencies", "other"]

[shilman]

Kind of confusing, but I guess it's OK.

Is there anything that the throw new Error was protecting us against that we are no longer protected from? Is there some other way to handle that case?

[tmeasday]

Yeah, I guess the code path is pretty weird, it's like:

1. Input all RHS of import lines in the MDX file
2. Search for all known entries that could be those imports
3. Then search over them for any that are stories.

I'm not quite sure why there are two loops. I'll refactor.

[tmeasday]

And, no, I don't think it was protecting us from anything. It was a "if this is missing something weird is going on" type throw, not a "we expect this to fail in certain circumstances".

[shilman]

@tmeasday looks like your refactor broke something in CI