[test][NFC] Change from nose to pytest (analyzer library)

[Szelethus]

Mind that this PR only affects the analyzer library, the others still rely on nose!

Motivation, why pytest

Nose is no longer supported, it is not compatible with python3.9 or newer, and will never be:
nose-devs/nose#1099 (comment)

As python3.10 is the oldest python version available from Ubuntu22.04's package manager by default, it is time to migrate.

We never really relied on nose features (as far as I can tell, we never actually import anything from the nose package), so this change isn't particularly painful (don't let the size of the change fool you, its pretty much just moving code around!). Pytest seems to be the industry standard framework lately, and supports most nose constructs out of the box.

The aim of this change that from the make target side, nothing changes -- you still run analyzer tests with make analyzer, and a specific test file with (having 'functional/skip' as the example):

TEST=tests/functional/skip make test_analyzer_feature

This is basically how granular nose could get. If you wanted to run a specific test case in a test file, you couldn't do that, but you can with pytest:

pytest analyzer/tests/functional/skip -v -k test_analyze_header_with_file_option

Mind that there are many environmental variables that need to be set in addition to the above command, so we need to write new make targets to make this user-friendly, but nevertheless, it is possible.

What changed

Broadly speaking, the change can be divided into 4 parts:

1. Replacing nose with pytest in the makefiles
2. Replacing nose config files with pytest files
3. Replace setup_package/teardown_package with setup_class/teardown_class, and setup/teardown to setup_method and teardown_method.
4. Fix up individual test environments under analyzer/tools.

For the Makefile and config changes, I hope they are self explanatory. Pytest is a rather painless drop-in replacement on the invocation side.

On the conversion, there is a page that discusses how one can convert nose to pytest:
https://docs.pytest.org/en/7.1.x/how-to/nose.html
It is stated (and is true) that pytest supports most, but not quite all features in nose. {setup, teardown}_package is not supported, but it turns out that we dedicate a package to every test class, so simply switching to {setup, teardown}_class was sufficient. That accounts for the vast majority of the code change. That is the only meaningful structural change -- setup->setup_method and the teardown variant was really just a simple rename.

At last, you can notice that some __init__.py files are copied over from analyzer/test/__init__.py. Frankly, I'm not sure how the tests worked previously without these files setting up these variables properly, but this skeleton fell out of the closet now.

[bruntib]

This is a great improvement, I like this change a lot! The modifications look good to me, so it is close to be merged.

We have some scripts which generate a template test in case someone wants to introduce a new one:
https://github.com/Ericsson/codechecker/tree/master/scripts/test
https://github.com/Ericsson/codechecker/tree/master/web/tests/functional/func_template.
Could you, please, apply these changes in the templates too? Maybe this will only be relevant when the web tests are migrated too.

Thank you!

[bruntib]

On the other hand it can be useful many times that the failed test is right at the end of all verbose logs and you don't need to waste time by locating them in a many megabytes long log message. I agree, though, that pytest is presenting errors much nicer and the localization of errors is much easier.

[Szelethus]

If you would like to check out how the output (without colors) looks like: https://github.com/Ericsson/codechecker/actions/runs/5122929933/jobs/9212716021?pr=3926