Use py_binary for script execution

[furtib]

Why:
We should rely on Bazel to run Python scripts and not hack them together ourselves.

What:

• Created a py_binary target for codechecker_script.py
• Created a py_binary target for per_file_script.py
• Replaced expand_template with environment variables in codechecker rule
• Replaced expand_template with arguments in per_file rule (use_default_shell_env = True, does not allow us to define env variables)

Addresses:
none