Cleans old JS, CSS and Webpack files from /src so they are not automatically copied to /build when running `grunt build`. Fixes errors that may be caused by copying outdated files and/or directories to /build.
Props: desrosj, isabel_brison, SergeyBiryukov, ironprogrammer, mukesh27, robinwpdeveloper, razthee007, costdev, peterwilsoncc, azaozz.
Fixes: #47749.
Built from https://develop.svn.wordpress.org/trunk@55484
git-svn-id: http://core.svn.wordpress.org/trunk@55017 1a063a9b-81f0-0310-95a4-ce76da25c4cd
Adds styles for individual core blocks to make it possible to render only styles for those blocks that are rendered on the page (frontend). This is optinal functionality for start that can be controlled with the new `separate_core_block_assets` filter.
In addition to that, styles can be inlined when `path` is passed when registering an individual styles. This functionality can be changed with the new `styles_inline_size_limit` filter. The maximum size of inlined styles in bytes defaults to 20 000.
Props aristath, aduth, westonruter, mcsf.
Fixes#50328, #52620.
Built from https://develop.svn.wordpress.org/trunk@50836
git-svn-id: http://core.svn.wordpress.org/trunk@50445 1a063a9b-81f0-0310-95a4-ce76da25c4cd
