[FEATURE] Migrate Extension-related signals to PSR-14 events

This change migrates all left-over signals in TYPO3 Core to PSR-14-compatible
events.

Package manager - related events have been moved to EXT:core to decouple
ExtensionManager functionality from PackageManager.

The following signals have been moved to events:
PackageManagement::packagesMayHaveChanged => PackagesMayHaveChangedEvent
InstallUtility::afterExtensionInstall => AfterPackageActivationEvent
InstallUtility::afterExtensionUninstall => AfterPackageDeactivationEvent
InstallUtility::afterExtensionT3DImport => AfterExtensionStaticDatabaseContentHasBeenImportedEvent
InstallUtility::afterExtensionStaticSqlImport => AfterExtensionStaticDatabaseContentHasBeenImportedEvent
InstallUtility::afterExtensionFileImport => AfterExtensionFilesHaveBeenImportedEvent
ExtensionManagementService::willInstallExtensions => BeforePackageActivationEvent
ProcessAvailableActionsViewHelper::processActions => AvailableActionsForExtensionEvent

Next up: Deprecate signal slot dispatcher.

Resolves: #90249
Releases: master
Change-Id: If688265c50c4200983c34f408b1cfd063f72546b
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/63045


Tested-by: TYPO3com <noreply@typo3.com>
Tested-by: Susanne Moog <look@susi.dev>
Tested-by: Andreas Fernandez <a.fernandez@scripting-base.de>
Reviewed-by: Susanne Moog <look@susi.dev>
Reviewed-by: Andreas Fernandez <a.fernandez@scripting-base.de>