Fix is_frozen, get_core_path(), get_gui_path() when cx_freeze is used for building binaries

[kozlovsky]

This PR fixes #8000.

First, it fixes the logic of is_frozen() and several functions that return base paths for resources (such as get_logger_config_path()).

Second, it fixes an issue with function naming: Currently, in Tribler we have two different functions with the same name get_base_path() that return different results:

• One function is defined in tribler/core/utilities/install_dir.py and returns "some" base directory; that exact meaning of the directory is different when Tribler runs from sources and when it runs as a binary. It is only used by another function, get_lib_path(), which is defined in the same module.
• Another function with the same name get_base_path() is defined in tribler/gui/utilities.py and returns base directory for GUI-related resources.

To avoid confusion and re-use the common logic, this PR renames and reactors the mentioned functions in the following way:

• get_base_path() from tribler.core.utilities.install_dir keeps its name, but now it always returns the directory that contains core / gui subdirectories.
• get_lib_path() is renamed to get_core_path() and returns the core directory as before.
• get_base_path() from tribler/gui/utilities is renamed to get_gui_path() and returns the gui directory as before.

Now all three functions get_core_path(), get_gui_path(), get_logger_config_path() internally use get_base_path() to avoid code duplication.