POC: Implement OWASP security logging.

[blackboxsw]

Provide an initial spike for logging OWASP formatted events in cloud-init for discussion. Integration tests will be added upon agreement for security logging procedures.

Proposed Commit Message

    feat: add OSWAP security event logging for user creation and system restart
    
    Implement OWASP structured logs in /var/log/cloud-init-security.log.
    
    Add security-related operations performed by cloud-init on behalf
    of user-data or platform meta-data:
    - user creation
    - user password change
    - system restart
    - system shutdown
    
    Default security log file can be changed by setting an alternative value
    for security_log_file in /etc/cloud/cloud.cfg(.d/*.cfg).

Additional Context

Test Steps

TODO: extend integration tests once initial discussion conclused

Merge type

• Squash merge using "Proposed Commit Message"
• Rebase and merge unique commits. Requires commit messages per-commit each referencing the pull request number (#<PR_NUM>)