[TASK] Change PHP namespace of EXT:mediace to FoT3

The PHP namespace for all PHP classes of EXT:mediace
is changed to "FoT3" as this code will be maintained by
the TYPO3 community under

https://github.com/FriendsOfTYPO3/mediace

Resolves: #71076
Releases: master
Change-Id: I4b14576bafcb3f4846a586c03ffc25ff2ac31384
Reviewed-on: https://review.typo3.org/44321


Reviewed-by: Helmut Hummel <helmut.hummel@typo3.org>
Tested-by: Helmut Hummel <helmut.hummel@typo3.org>
Reviewed-by: Michael Oehlhof <typo3@oehlhof.de>
Tested-by: Michael Oehlhof <typo3@oehlhof.de>
Reviewed-by: Gernot Schulmeister <gernotschulmeister@gmx.at>
Tested-by: Gernot Schulmeister <gernotschulmeister@gmx.at>
Reviewed-by: Benni Mack <benni@typo3.org>
Tested-by: Benni Mack <benni@typo3.org>