Decompress revision text

Revision text gzip-saved (via Revision::compressRevisionText()) was not being
decompressed (resulting in garbled output)

Meanwhile, I don't really see why find() needs its own code; it does exactly
what findMulti() does, so no need to duplicate that code.

Depends on https://gerrit.wikimedia.org/r/#/c/78079/, which introduces
Revision::decompressRevisionText()

Conflicts:
	includes/Data/ObjectManager.php
	includes/Data/RevisionStorage.php

Change-Id: I82a5f68dde312fbb5cb6ce60fe46234a23f7a3b0