[BUGFIX] Flush opcode caches while saving PHP files.

After manipulating PHP files, which we include with "require" we should
clear the opcode cache, if there is one installed.

So we introduce OpcodeCacheUtility to handle the clearing of the opcode
cache. Also to have a way to give feedback to the install tool which
can show the quality of the opcode cache in use. It also checks if an
opcode cache is enabled in the configuration, not only if the extension
is installed.

Use of this opcode cache clearing is added to the ConfigurationManager,
PackageManager and the cache (Simple)FileBackend.

Make use of this data in the SystemEnvironmentCheck.

Resolves: #55252
Releases: 6.2, 6.1, 6.0
Change-Id: I881f3fbe055c9566663c2c3c238de62ae30f7149
Reviewed-on: https://review.typo3.org/27024
Reviewed-by: Markus Klein
Tested-by: Markus Klein