Add automation config snapshot debugging feature

[nammn]

Summary

Add debug-only automation config snapshot feature to track AC changes step-by-step. When MDB_AC_SNAPSHOT=true is set on the operator pod, each PUT to the automationConfig endpoint is captured as a numbered diff in a <resource-name>-ac-snapshot ConfigMap.

Why: Debugging complex AC change sequences (like auth migrations) requires visibility into what changed between each reconcile step. Current logging doesn't preserve the full change history.

What:

• Add HTTP client hook to capture successful PUT requests
• Compute diffs between consecutive AC versions using r3labs/diff
• Filter out auto-managed fields (mongodbVersions, builds, etc.)
• Store numbered steps in ConfigMap for inspection

Proof of Work

ConfigMap created with step-by-step diffs showing X.509 → SCRAM-256 migration:

• step-001: Initial AC structure created
• step-002: Auth made authoritative
• step-003: X.509 auth enabled
• step-004: Replica set and processes added
• step-005: SCRAM-256 added to deployment auth mechanisms
• step-006: TLS mode relaxed to OPTIONAL
• step-007: Auth disabled
• step-008: Switched to SCRAM-256 (removed X.509, added autoPwd)

Full ConfigMap output validates the feature works end-to-end.

Checklist

• Have you linked a jira ticket and/or is the ticket in the title?
• Have you checked whether your jira ticket required DOCSP changes?
• Have you added changelog file?
  • use skip-changelog label if not needed
  • refer to Changelog files and Release Notes section in CONTRIBUTING.md for more details