Adds logic that fixes the limitation for souces by allowing merging the `uses_context` defined by block bindings sources into supported block types. Each source defines the context it needs and it is added to the block types that are using the block bindings API.
Fixes#60525.
Props santosguillamot, gziolo, czapla, thekt12.
Built from https://develop.svn.wordpress.org/trunk@57641
git-svn-id: http://core.svn.wordpress.org/trunk@57142 1a063a9b-81f0-0310-95a4-ce76da25c4cd