[BUGFIX] Make CodeMirror search persistent

Currently, when searching a term in CodeMirror (used in EXT:t3editor),
the search bar disappears when after the operation, which is super
annoying.

The configuration of CodeMirror is slightly changed to keep the
search bar always present until closed explicitly.

Resolves: #88162
Releases: master, 9.5
Change-Id: I8780d9b10816c1667c14b0a23f50428a5f081579
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/60490


Tested-by: TYPO3com <noreply@typo3.com>
Tested-by: Josef Glatz <josefglatz@gmail.com>
Tested-by: Sven Juergens <typo3@blue-side.de>
Tested-by: Richard Haeser <richard@maxserv.com>
Reviewed-by: Josef Glatz <josefglatz@gmail.com>
Reviewed-by: Sven Juergens <typo3@blue-side.de>
Reviewed-by: Richard Haeser <richard@maxserv.com>