feat(secrets): improve timing git history

[marynaKK]

• added skip file list for skipping .md files in githistory
• moved static functions to a class in GitHistoryScanner
• added root folder in the git command:

base_diff_format = f'diff --git {root_folder}/{file_diff.a_path} {root_folder}/{file_diff.b_path}' \
                   f'\nindex 0000..0000 0000\n--- {root_folder}/{file_diff.a_path}\n+++ {root_folder}/{file_diff.b_path}\n'

Checklist:

• My code follows the style guidelines of this project
• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• I have added tests that prove my feature, policy, or fix is effective and works
• New and existing tests pass locally with my changes
• Any dependent changes have been merged and published in downstream modules

[omryMen]

don't see a reason to save it in the class as it's being used once to trasfer from history store to secret store