Unit tests: Fix problematic nasty hack in run_tests

[jrohel]

Closes: #1947

I found a nasty hack in the code. A pointer to the CPPUnit::TestCaller class was cast to a pointer to HackTestCaller using reinterpret_cast. The hack was used to make private members accessible in the original class for LogCaptureListener.
Additionally, BaseTestCase has been modified in the LogCaptureListener class.

The code has been rewritten to not need this hack. And the BaseTestCase modification was moved to
the BaseTestCase::setUp method.

Solves:

    Start  1: test_libdnf
1/3 Test  #1: test_libdnf ......................***Failed    4.64 sec
/dnf5/test/libdnf5/run_tests.cpp:69:53: runtime error: member access
 within address 0x50800001a7a0 which does not point to an object of type 'HackTestCaller'
0x50800001a7a0: note: object is of type 'CppUnit::TestCaller<AdvisoryAdvisoryModuleTest>'
 00 00 00 00  a0 7d c1 01 00 00 00 00  30 7e c1 01 00 00 00 00  90 c3 01 00 40 50 00 00  29 00 00 00
              ^~~~~~~~~~~~~~~~~~~~~~~
              vptr for 'CppUnit::TestCaller<AdvisoryAdvisoryModuleTest>'

ERROR: LeakSanitizer: detected memory leaks

Direct leak of 128 byte(s) in 2 object(s) allocated from:
    #0 0x7f19b32c17d8 in realloc.part.0 (/lib64/libasan.so.8+0xc17d8)
     (BuildId: 5294bd2731fcae07af92dfea7808576c57d53bc9)
    #1 0x7f19b261e242 in d_growable_string_callback_adapter
     (/lib64/libstdc++.so.6+0x1e242)

SUMMARY: AddressSanitizer: 128 byte(s) leaked in 2 allocation(s).