TinyMCE was adding attributes to <br> elements within code blocks which
would then not be converted to newlines by our code regex match.
This changes the conversion to use dom querying instead.
Fixes#3507
Sets sizes on WYSIWYG code block sections based on content lines
as an early pre-codemirror height prediction to avoid excessive
jumping in the editor.
For #3326
- Fixed issues with new code blocks breaking or acting odd due to
misnamed contenteditable attribute.
- Helped fix issue where code blocks may show in a strage blank state
due to timing within shadow dom loading.
- Fixed some function timing issues where some functions required their
async predecessor to have finished.
Tested rather heavily in firefox and brave.
Fixes#3292
Code blocks in tinymce could sometimes end up exploded into the sub
elements of the codemirror display.
This changes the strategy to render codemirror within the shadow dom of
a custom element while preserving the normal pre/code DOM structure.
Still a little instability when moving/adding code blocks within details
blocks but much harder to break things now.
- Split everything into specific plugin/concern files to make things
more managable. Means original component file is now simple and much
of the core config is focused in one place.
