Add B901 plugin: detect unsafe yaml.load/full_load usage

[ROSPL07]

What I Did

• Added new plugin (B901) to detect unsafe usage of yaml.load, yaml.full_load, or yaml.unsafe_load.
• Flags calls where Loader is not safe (e.g., FullLoader, Loader).
• Added example file for testing.

Why

• Unsafe YAML loading is a known Remote Code Execution risk.
• This helps developers migrate to yaml.safe_load.

Impact

• Improves static analysis coverage.
• No breaking changes, safe to merge.

[ericwb]

We already have coverage for yaml.load. Please see:

https://bandit.readthedocs.io/en/latest/plugins/b506_yaml_load.html
https://github.com/PyCQA/bandit/blob/main/bandit/plugins/yaml_load.py

[sigmavirus24]

We probably just need to fold some of the additions here into that set of checks. Would you be willing to do that @ROSPL07 ?

[ROSPL07]

We probably just need to fold some of the additions here into that set of checks. Would you be willing to do that @ROSPL07 ?

Sure, please share me the details.