Improve coding style

Description

I have reformatted the Python code in this project using yapf, following Google's conventions and minimizing changes to the code as much as possible. Additionally, I have created a .git-blame-ignore-revs file to address the issue with git blame that was raised in PR #79.

If there are certain parts of your code that you do not want to be formatted, you can use # yapf: disable and # yapf: enable to wrap them. For example, I have disabled auto formatting for the __slots__ of NFlow. https://github.com/ssrtw/nfstream/blob/add-formatter/nfstream/flow.py#L113

Type of change

Please delete options that are not relevant.

[ ] Bug fix (non-breaking change which fixes an issue)
[ ] New feature (non-breaking change which adds functionality)
[ ] Breaking change (fix or feature that would cause existing functionality to not work as expected)
[ ] This change requires a documentation update

How Has This Been Tested?

Using the tests.py script

Test Configuration:

OS version: Linux 5.19.0-32-generic 22.04.1-Ubuntu x86_64
Python version: 3.11.2
Hardware:
- CPU: Intel i7-13700kf
- RAM: DDR4-32GB-3200

Checklist:

[x] My code follows the style guidelines of this project
[x] 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
[x] My changes generate no new warnings
[ ] I have added tests that prove my fix is effective or that my feature works
[x] New and existing unit tests pass locally with my changes
[ ] Any dependent changes have been merged and published in downstream modules
[x] I have checked my code and corrected any misspellings

nfstream / nfstream