Fix #1181 Add port property to installerOptions in the HTTPReceiver

[seratch]

Summary

This pull request resolves #1181 by adding custom port option in the App/HTTPReceiver constructors. Also, while working on this, the SocketModeReceiver starts its underlying HTTP server for the OAuth flow (before start() method call). As I believe that the timing to start the HTTP server should be consistent with other receivers, I've changed the behavior too.

Fixes #1181
Fixes #1179

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.

[codecov]

Codecov Report

Merging #1184 (431d890) into main (3077c40) will increase coverage by 0.09%.
The diff coverage is 54.54%.

❗ Current head 431d890 differs from pull request most recent head bd1f71f. Consider uploading reports for the commit bd1f71f to get more accurate results

@@            Coverage Diff             @@
##             main    #1184      +/-   ##
==========================================
+ Coverage   71.33%   71.42%   +0.09%     
==========================================
  Files          17       17              
  Lines        1399     1414      +15     
  Branches      415      424       +9     
==========================================
+ Hits          998     1010      +12     
- Misses        331      332       +1     
- Partials       70       72       +2     

Impacted Files	Coverage Δ
src/receivers/HTTPReceiver.ts	37.08% <11.11%> (-0.96%)	⬇️
src/receivers/SocketModeReceiver.ts	88.63% <80.00%> (-0.65%)	⬇️
src/App.ts	85.05% <100.00%> (+1.41%)	⬆️

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[filmaj]

Thanks for all your hard work on this! Looks good 👍

[seratch]

Thank you for your quick review!