[BUGFIX] PackageManager initialize() signature is incompatible

PackageManagerInterface contains following method declaration:

 public function initialize(\TYPO3\Flow\Core\Bootstrap $bootstrap);

however in the PackageManager the signature is:

  public function initialize(\TYPO3\Flow\Core\Bootstrap $bootstrap,
    $packagesBasePath = FLOW_PATH_PACKAGES,
    $packageStatesPathAndFilename = '')

This will create a fatal error on some versions of php and when running
unit tests on hhvm (of CMS), see
http://php.net/manual/en/language.oop5.interfaces.php

"The class implementing the interface must use the exact same method
signatures as are defined in the interface. Not doing so will result
in a fatal error."

This change updates the method signature of the PackageManager to be in
line with the interface.

Resolves: #56660
Related: #56409
Releases: 6.2
Change-Id: Iab7ae0d6d9809abe7cb6f9b73adb77f06d2f0820
Reviewed-on: https://review.typo3.org/28195
Reviewed-by: Thomas Maroschik
Reviewed-by: Sebastian Müller
Reviewed-by: Sebastian Fischer
Reviewed-by: Steffen Ritter
Tested-by: Steffen Ritter
Reviewed-by: Markus Klein
Tested-by: Markus Klein