security: replace unsafe YAML loading with safe_load to prevent RCE

[RinZ27]

The current implementation in okta/okta_configuration.py utilizes yaml.load with potentially
unsafe loaders, which is vulnerable to arbitrary code execution during deserialization of
untrusted YAML input.

Technical Root Cause:
Unsafe loaders (like yaml.Loader or yaml.CLoader) allow the instantiation of any Python object,
providing a direct vector for Remote Code Execution (RCE). Automated analysis has flagged this as
a critical security risk when processing configuration files.

Changes:

• Migrated from yaml.load to yaml.safe_load to restrict deserialization to standard YAML types
  only.
• Streamlined imports and removed unnecessary unsafe loader logic.
• Implemented proper file context management using with statement for better resource handling.

This hardening measure eliminates a critical attack vector and aligns the SDK with modern security
standards for data serialization.

[RinZ27]

Ping on this. It replaces unsafe YAML loading with safe_load to mitigate potential RCE risks during configuration parsing. Given the security implications, mind having a look? Thanks!

[RinZ27]

I'm checking back on this PR as it addresses a potential RCE vulnerability by switching to safe_load. I noticed the repo was updated recently and I've verified that my changes are still mergeable without conflicts. @BinoyOza-okta @agrja-rastogi-okta, would you mind taking a look when you have a moment? Thanks!