Remove get_default_block_editor_settings from theme JSON resolver

[Mamaduka]

Context:

The issue, is that the function get_default_block_editor_settings is called. This
function returns an array of data, including lots of information needed for the
editor. But in this context, json resolved is getting lots of data is that is never
used. As this method is call 200-500 times per page load, it results in all these
calls to get_option, is_rtl and get_allowed_mime_types, data is never used. This
functions have serious overhead, as all of them have filters and some even database
queries attached to them. As this function is called on the front end, this results
in 11-15% of extra page load.

See ​https://github.com/WordPress/gutenberg/pull/46112

Trac ticket: https://core.trac.wordpress.org/ticket/57547
Gutenberg PR: ​https://github.com/WordPress/gutenberg/pull/46112

[hellofromTonya]

Adding keyword for backport tracking.

### Before

### After

Performance improvement 👍

Updated the function name and added simple unit tests.

Good catch. Thank you, @felixarntz!

Thank you, @mukeshpanchal27!

[flixos90]

In 55146:

Themes: Avoid unnecessary database queries from get_default_block_editor_settings() in WP_Theme_JSON_Resolver::get_theme_data().

The get_default_block_editor_settings() function included several pieces of data that are irrelevant for the purpose that WP_Theme_JSON_Resolver was calling it for, yet resulted in three database queries on page load that can be avoided.

This changeset introduces a new function get_classic_theme_supports_block_editor_settings() to takes responsibility of only the data needed in WP_Theme_JSON_Resolver, which now uses that function. This leads to a reduction of database queries and accordingly a performance improvement.

Props mamaduka, spacedmonkey, oandregal, flixos90, audrasjb, mukesh27.
Fixes #57547.

Committed in https://core.trac.wordpress.org/changeset/55146 🎉