attachment_url_to_postid() fails if url protocols don't match

[welcher]

If attachment_url_to_postid() is passed a url with a protocol that does not match the upload directory url protocol the substr() call does not remove the appropriate part of the url and the subsquent database lookup does not retrieve the ID correctly and the method returns 0. I discovered this when working with a client site that had an http front end but an https backend.

I have attached the unit tests and fix patches separately so the issue can be seen before applying the fix which resolved the issue.

[welcher]

Unit Tests

[welcher]

Patch file

[obenland]

We're a few days away from RC, let's do this in a future release.

[welcher]

Refreshed unit tests patch.

[welcher]

Added a refreshed patch for the unit tests the other patch applied cleanly for me.

[wonderboymusic]

In 33705:

Ensure that attachment_url_to_postid() matches cross-scheme when front-end and back-end schemes are different.

Adds unit test.

Props welcher.
Fixes #33109.