feat(cdk-experimental/selection): Merge cdk–selection to the master

[yifange]

Merge the cdk-selection branch to the master branch #18581

[jelbourn]

LGTM

(this code has all been previously reviewed on the cdk-selection branch)

[jelbourn]

Caretaker note: we should fixup the commit messages while also preserving the individual comments

[andrewseguin]

Please rebase and then stick the "merge ready" label back on

[yifange]

I resolved the conflicts in Github's UI and it seems it created a merge commit. It looks all good but let me know if you want me to do it in another way.

I added back "merge ready", not sure about "commit message fixup" though.

[andrewseguin]

Unfortunately our script isn't able to preserve commits while also needing to fix some up.

I re-attempted your rebase and we should be good. Once the CI reports green then we can get this in

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