Fix #1038 by adding admin.auth.policy.* API support

[seratch]

Summary

This pull requests fixes #1038 by adding admin.auth.policy.* API support. Refer to the issue for details.

Category (place an x in each of the [ ])

• slack_sdk.web.WebClient (sync/async) (Web API client)
• slack_sdk.webhook.WebhookClient (sync/async) (Incoming Webhook, response_url sender)
• slack_sdk.socket_mode (Socket Mode client)
• slack_sdk.signature (Request Signature Verifier)
• slack_sdk.oauth (OAuth Flow Utilities)
• slack_sdk.models (UI component builders)
• slack_sdk.scim (SCIM API client)
• slack_sdk.audit_logs (Audit Logs API client)
• slack_sdk.rtm_v2 (RTM client)
• /docs-src (Documents, have you run ./docs.sh?)
• /docs-src-v2 (Documents, have you run ./docs-v2.sh?)
• /tutorial (PythOnBoardingBot tutorial)
• tests/integration_tests (Automated tests for this library)

Requirements (place an x in each [ ])

• I've read and understood the Contributing Guidelines and have done my best effort to follow them.
• I've read and agree to the Code of Conduct.
• I've run python3 -m venv .venv && source .venv/bin/activate && ./scripts/run_validation.sh after making the changes.

[codecov]

Codecov Report

Merging #1039 (8678d09) into main (3fcdbe1) will decrease coverage by 0.06%.
The diff coverage is 78.26%.

@@            Coverage Diff             @@
##             main    #1039      +/-   ##
==========================================
- Coverage   84.38%   84.31%   -0.07%     
==========================================
  Files          95       95              
  Lines        8869     8938      +69     
==========================================
+ Hits         7484     7536      +52     
- Misses       1385     1402      +17     

Impacted Files	Coverage Δ
slack_sdk/web/async_client.py	93.93% <78.26%> (-0.49%)	⬇️
slack_sdk/web/client.py	95.38% <78.26%> (-0.54%)	⬇️
slack_sdk/web/legacy_client.py	95.25% <78.26%> (-0.54%)	⬇️
slack_sdk/socket_mode/builtin/client.py	79.19% <0.00%> (-0.68%)	⬇️
slack_sdk/socket_mode/builtin/connection.py	35.71% <0.00%> (-0.43%)	⬇️

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update 3fcdbe1...8678d09. Read the comment docs.

[seratch]

Thanks for the review!