[stable29] Add bidirectional text support - Backend #9100

Job	Run time
changes	12s
php8.0-webdav	4m 11s
php8.1-webdav	2m 3s
php8.2-webdav	3m 41s
php8.3-webdav	3m 47s
files-external-webdav-summary	5s
	13m 59s

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