feat: add Azure OpenAI Assistant API support for custom-copilot Python template

[frankqianms]

workitem: https://msazure.visualstudio.com/Microsoft%20Teams%20Extensibility/_workitems/edit/28871758/?workitem=28955069

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 89.48%. Comparing base (02a1222) to head (040e79d).
Report is 2 commits behind head on dev.

Additional details and impacted files

@@           Coverage Diff           @@
##              dev   #12153   +/-   ##
=======================================
  Coverage   89.48%   89.48%           
=======================================
  Files         572      572           
  Lines       33621    33629    +8     
  Branches     6421     6467   +46     
=======================================
+ Hits        30085    30093    +8     
  Misses       1583     1583           
  Partials     1953     1953           

Files	Coverage Δ
packages/fx-core/src/question/create.ts	91.19% <100.00%> (+0.01%)	⬆️

... and 3 files with indirect coverage changes