[TASK] Use @inject annotation in extensionmanager

This patch removes all occurences of injectFooBar methods from the
extensionmanager sysext and replaces them with the @inject
annotation.

Releases: 6.2
Fixes: #50482
Change-Id: Idc55d15e3a4d6086529864e4013478983b9c45e7
Reviewed-on: https://review.typo3.org/22619
Reviewed-by: Christian Kuhn
Tested-by: Christian Kuhn
Reviewed-by: Wouter Wolters
Tested-by: Wouter Wolters