Restructures the examples build rules so that all examples are exposed
through a single file group in adev/src/content/examples.
Also adds a separate filegroup in the same location for just the
embeddable examples and adds it to the APPLICATION_FILES for the docs
app.
This uncovered the fact that some of our examples have broken
non-compiling code. I've excluded these ones from being embeddable for
now, until the breakages can be addressed
PR Close#60778
Restores the ability to have example components rendered alongside the
code. This functionality was broken a while back by #53511.
To enable the embedded preview for an example, add `preview` and
`path=adev/src/content/expamples/component/to/render.ts` attributes to
the `<docs-code>` or `<docs-code-multifile>` tag.
Tested with one of the accessibility examples and it seems to work now.
PR Close#60778
