feat: declarative copilot with plugin from existing api

[yuqizhou77]

Task 28810109: declarative copilot with plugin from spec

• User now can scaffold a declarative Copilot project + api plugin from exisiting API.
• Update the basic api plugin template so that there is no need for multiple templates. Use "filterFn" to control whether to include DC related files and updating several files to ".tpl" so that the generated content will match DC + plugin or DC only

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 89.44%. Comparing base (adc6a89) to head (3256686).
Report is 1 commits behind head on dev.

Additional details and impacted files

@@            Coverage Diff             @@
##              dev   #12095      +/-   ##
==========================================
+ Coverage   89.42%   89.44%   +0.02%     
==========================================
  Files         570      570              
  Lines       33604    33554      -50     
  Branches     6460     6590     +130     
==========================================
- Hits        30049    30014      -35     
+ Misses       1588     1583       -5     
+ Partials     1967     1957      -10     

Files	Coverage Δ
...-core/src/component/generator/apiSpec/generator.ts	96.22% <100.00%> (+6.27%)	⬆️
packages/fx-core/src/question/create.ts	91.17% <ø> (ø)

... and 1 file with indirect coverage changes