Allow view access of template rest endpoint to anyone with the edit_post capability

[fabiankaegy]

Sync ticket for ​https://github.com/WordPress/gutenberg/pull/60317

In order to render the block template in the locked template preview inside the post editor we need to be able to fetch the contents of any block templates/template parts for any user role that can edit a post.

Trac ticket: https://core.trac.wordpress.org/ticket/61137

[fabiankaegy]

I added some unit test cases that cover the changes in the flow

[fabiankaegy]

@youknowriad and @TimothyBlynJacobs since you worked on this one with me / reviewed in Gutenberg, would you be able to help get it into core also? We have 1 week till Beta 1 is supposed to be released and I want to make sure we have time for any remediation in case your review wants to change anything.

Thanks in advance :)

I'll add this to my commit list if no one beats me to it.

I have committed this PR (you can see the commit in Github on trunk) but there might be an issue currently in Trac preventing the changeset link from working https://core.trac.wordpress.org/changeset/58227

[youknowriad]

closed by https://core.trac.wordpress.org/changeset/58227

[swissspidy]

In 58229:

REST API: Remove default text domain from translatable strings after [58227].

See #61137.

Follow-up commit: https://core.trac.wordpress.org/changeset/58229

[gziolo]

In 58232:

Tests: Update the generated fixture for REST API

Follow-up [58227].
See #61137.