[TASK] Increase code coverage of SignalSlot/Dispatcher

Added some missing tests to achieve 100% code coverage.
Also adjusted the copyright header and author annotations.

Releases: 6.1
Resolves: #44611
Change-Id: I9ffb474b5cd44d30c9eff49ae37ab55f5f68a5ce
Reviewed-on: https://review.typo3.org/17580
Reviewed-by: Wouter Wolters
Tested-by: Wouter Wolters
Reviewed-by: Alexander Schnitzler
Tested-by: Alexander Schnitzler
[TASK] Increase code coverage of Service/TypeHandlingService

Added one missing tests to achieve 100% code coverage.
Also adjusted the copyright header.

Releases: 6.1
Resolves: #44612
Change-Id: If543b055c139d63edcb8960e7e0f89875017bdf3
Reviewed-on: https://review.typo3.org/17581
Reviewed-by: Wouter Wolters
Tested-by: Wouter Wolters
Reviewed-by: Alexander Schnitzler
Tested-by: Alexander Schnitzler
[TASK] Increase code coverage of FrontendConfigurationManager

Releases: 6.1
Resolves: #44656
Change-Id: If39fb33a3a3d4cffca3f74f5f15d4a44ebf0e152
Reviewed-on: https://review.typo3.org/17593
Reviewed-by: Wouter Wolters
Tested-by: Wouter Wolters
Reviewed-by: Anja Leichsenring
Tested-by: Anja Leichsenring
[TASK] Improve code coverage of Scheduler/FieldProvider

* Also fixed a small bug in Cli/Command.php

Releases: 6.1
Resolves: #44650
Change-Id: Ic9cc4ebb81a3926415223f6a7a8078198a39f1ab
Reviewed-on: https://review.typo3.org/17592
Reviewed-by: Wouter Wolters
Tested-by: Wouter Wolters
Reviewed-by: Anja Leichsenring
Tested-by: Anja Leichsenring
Revert "[FEATURE] Allow different overriding of object mapping per plugin"

This reverts commit fecb7b1b32629283aa932cde38bdd26ee94dcf8d.

Releases: 6.1
Change-Id: I448b1fd0638a86ab31705be1c87056bc082b0dc8
Reviewed-on: https://review.typo3.org/17597
Reviewed-by: Alexander Schnitzler
Tested-by: Alexander Schnitzler