Avoid using "FSE" in function-names and inline docs

[aristath]

"FSE" was a term used in the initial development stages on Full Site Editing in the Gutenberg plugin. However, these terms bled into function-names and inline docs.
We should remove references to FSE since this is not what it will be called.
This should change prior to 5.8 because once functions get in, it will be extremely hard to remove them without adding deprecations & aliases.

This is a companion to ​https://github.com/WordPress/gutenberg/pull/32950, renaming fse references

Trac ticket: https://core.trac.wordpress.org/ticket/53497#ticket

[jorbin]

I think the inline docs piece of this change is fine, but as @desrosj notes on the patch, guteberg_is_fse_theme is a function that will exist in released versions of Gutenberg, so I don't think that we can remove that reference.

[desrosj]

I'm going to commit the documentation changes and close this one out. We will need to add an additional function_exists() check if the function name is changed in ​Gutenberg-32950.

[desrosj]

In 51251:

Themes: Remove mention of “FSE” in Core.

Props aristath, jorbin.
Fixes #53497.

Merged into Core in https://core.trac.wordpress.org/changeset/51251.

[desrosj]

I found one more instance while reviewing the unit tests for #53497. The theme used to test block theme features is called fse. I think this can just be renamed to block-theme. Patch incoming.

Trac ticket: https://core.trac.wordpress.org/ticket/53497

Trac ticket: https://core.trac.wordpress.org/ticket/53497

[desrosj]

In 51370:

Themes: Remove mention of “FSE” in Core.

“FSE” themes are block themes.

Fixes #53497.

Merged into Core in https://core.trac.wordpress.org/changeset/51370.

[desrosj]

Marking [51370] for backport.

[desrosj]

In 51371:

Tests: Add missed file update in [51370].

See #53497.

[SergeyBiryukov]

Looks good to backport.

When something like this comes up next time, it would be great to rename the directory to preserve commit history, instead of removing and re-adding :)

[desrosj]

Replying to SergeyBiryukov:

When something like this comes up next time, it would be great to rename the directory to preserve commit history, instead of removing and re-adding :)

Sounds good! I thought I had fixed that before committing, but I guess I did not. I'll triple check that in the future. :)

[desrosj]

In 51373:

Themes: Remove mention of “FSE” in Core.

“FSE” themes are block themes.

Props SergeyBiryukov.
Merges [51370-51371] to the 5.8 branch.
Fixes #53497.

[desrosj]

In 51374:

Themes: Remove mention of “FSE” in Core.

“FSE” themes are block themes.

Follow up to [51373].

Unprops desrosj.
Merges [51370-51371] to the 5.8 branch.
Fixes #53497.