Feature: #60123 - Unit base test case removes test files
See forge#60123
Description
Some unit tests need to create test files or directories to check the system
under test. Those files should be removed again.
A test can now register absolute file paths in $this->test, and
the generic tear method will then remove them. Only files, links and directories
within typo3temp/ are allowed.
Impact
This allows tests to clean up the environment without leaving obsolete test files behind.