[BUGFIX] Do not load LocalConfiguration in unit test bootstrap

The patch removes loadConfigurationAndInitialize() from unit test
bootstrap and substitutes it with some more fine grained bootstrap
calls. In effect, the instance specific LocalConfiguration.php is
no longer loaded and removes another depencency from unit tests
to the instance.

Change-Id: Ia6591fe8d40d530558a514832c8d649c46b4ccc9
Resolves: #57035
Related: #51436
Releases: 6.2
Reviewed-on: https://review.typo3.org/28491
Reviewed-by: Helmut Hummel
Tested-by: Helmut Hummel
Reviewed-by: Markus Klein
Tested-by: Markus Klein