Editor: Fix block template files query for a post-type

[Mamaduka]

Sync ticket for ​https://github.com/WordPress/gutenberg/pull/61244.

Fixes a bug where block template files that aren't defined in theme.json's customTemplates were missing from get_block_templates for a post-type query.

The custom template files with no associated post-types are available for all post-types.

Note: Original regression was introduced in r55687 but only started affecting Editor users in WP 6.5.

Sync ticket for ​https://github.com/WordPress/gutenberg/pull/61244.

Trac ticket: https://core.trac.wordpress.org/ticket/61110.

Thanks for testing, @creativecoder!

I added the explanatory comment for the data provider.

P.S. Comment support for JSON would have been handy at this moment :)

[grantmkin]

Noting here that there is discussion about the performance impact of this fix in the Gutenberg PR, starting with this comment: ​https://github.com/WordPress/gutenberg/pull/61244#issuecomment-2089797625

[jorbin]

It was discussed on the PR to punt this from 6.5.3 and I agree so moving to 6.6 and then it can get moved to 6.5.4 for later consideration.

See: ​https://github.com/WordPress/gutenberg/pull/61244#issuecomment-2090756404

Hey hey @Mamaduka, are we only missing an approval?

@vcanales that’s correct.

Checking blame to find people to review 😄

[ellatrix]

In 58323:

Editor: Fix block template files query for a post-type.

See ​https://github.com/WordPress/gutenberg/pull/61244.
See ​https://github.com/WordPress/wordpress-develop/pull/6468.

Fixes #61110.

Props mamaduka, mukesh27, grantmkin, vcanales, ellatrix, oandregal.

[ellatrix]

In 58324:

Editor: add missing test template file.

Add a missing file for r58323.

See ​https://github.com/WordPress/wordpress-develop/pull/6468.
See #61110.