Enable developers to pass fully implemented authorize along with installation_store

[seratch]

This pull request improves the initialization process to accept fully-implemented authorize along with oauth_settings. This enhancement is beneficial for advanced developers that understand what they are doing. Rejecting a simple function-based authorize is still helpful to avoid pitfalls for people new to bolt-python.

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

• slack_bolt.App and/or its core components
• slack_bolt.async_app.AsyncApp and/or its core components
• Adapters in slack_bolt.adapter
• Document pages under /docs
• Others

Requirements (place an x in each [ ])

Please read the Contributing guidelines and Code of Conduct before creating this issue or pull request. By submitting, you are agreeing to those rules.

• 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 ./scripts/install_all_and_run_tests.sh after making the changes.

[codecov]

Codecov Report

Merging #851 (5c244a5) into main (57cb043) will increase coverage by 0.00%.
The diff coverage is 100.00%.

@@           Coverage Diff           @@
##             main     #851   +/-   ##
=======================================
  Coverage   92.10%   92.10%           
=======================================
  Files         181      181           
  Lines        6089     6093    +4     
=======================================
+ Hits         5608     5612    +4     
  Misses        481      481           

Impacted Files	Coverage Δ
slack_bolt/app/app.py	87.50% <100.00%> (+0.05%)	⬆️
slack_bolt/app/async_app.py	94.45% <100.00%> (+0.02%)	⬆️

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