Improve keyboard control of Edit Selection mode in the media manager.

See #29326
Props adamsilverstein


git-svn-id: https://develop.svn.wordpress.org/trunk@30374 602fd350-edb4-49c9-b593-d223f7449a82
WPDB: When a `db.php` drop-in is being used, and it doesn't explicitly define itself as connecting to MySQL, skip the character set checks. This ensures that existing drop-ins won't accidentally run checks that they don't support.

See #21212.


git-svn-id: https://develop.svn.wordpress.org/trunk@30375 602fd350-edb4-49c9-b593-d223f7449a82
Improve Thickbox's close button so it can be announced by screen readers.

Fixes #29455
Props SergeyBiryukov


git-svn-id: https://develop.svn.wordpress.org/trunk@30376 602fd350-edb4-49c9-b593-d223f7449a82
Avoid re-registering the `keydown` event controller in the media grid so arrow controls don't skip media items.

Fixes #30348
Props UmeshSingla


git-svn-id: https://develop.svn.wordpress.org/trunk@30377 602fd350-edb4-49c9-b593-d223f7449a82
Update the inline docs for the `keyEvent` callback in the media grid.

Props adamsilverstein
See #29725


git-svn-id: https://develop.svn.wordpress.org/trunk@30378 602fd350-edb4-49c9-b593-d223f7449a82