Simplify `.htaccess` redirect ruleset

The .htaccess RewriteCond and RewriteRule looks kind of complicated:

https://github.com/nextcloud/server/blob/0b354efb22a05a061275c2bb1a9c715a70d074d8/lib/private/Setup.php#L570-L579

How about implementing a simpler ruleset.

E.g. see TYPO3 .htaccess for an idea:

https://github.com/TYPO3/typo3/blob/18dc58b93f75c64521f77f80fa42d1564b6b7eb7/typo3/sysext/install/Resources/Private/FolderStructureTemplateFiles/root-htaccess#L329-L334

	# If the file/symlink/directory does not exist => Redirect to index.php.
	# For httpd.conf, you need to prefix each '%{REQUEST_FILENAME}' with '%{DOCUMENT_ROOT}'.
	RewriteCond %{REQUEST_FILENAME} !-f
	RewriteCond %{REQUEST_FILENAME} !-d
	RewriteCond %{REQUEST_FILENAME} !-l
	RewriteRule ^.*$ %{ENV:CWD}index.php [QSA,L]

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Inspect lib/private/Setup.php around lines 570-579 and compare the proposed TYPO3 .htaccess ruleset with Nextcloud's current generated rules. Determine whether the simpler conditions preserve Nextcloud's routing behavior, then update the generated rules so nonexistent files, directories, and symlinks reach index.php without breaking existing requests.