refactor: rename apiPlugin to plugin

[yuqizhou77]

• rename "apiPlugins" to "plugins" as what has been finalized in schema.

[codecov]

Codecov Report

Attention: Patch coverage is 90.00000% with 1 lines in your changes are missing coverage. Please review.

Project coverage is 87.03%. Comparing base (b00041d) to head (49faad3).

Additional details and impacted files

@@            Coverage Diff             @@
##              dev   #11011      +/-   ##
==========================================
- Coverage   87.03%   87.03%   -0.01%     
==========================================
  Files         454      454              
  Lines       27096    27095       -1     
  Branches     5446     5445       -1     
==========================================
- Hits        23584    23583       -1     
  Misses       1768     1768              
  Partials     1744     1744              

Files	Coverage Δ
.../src/component/driver/teamsApp/createAppPackage.ts	90.96% <100.00%> (-0.06%)	⬇️
...src/component/generator/copilotPlugin/generator.ts	94.57% <100.00%> (ø)
packages/fx-core/src/question/create.ts	92.75% <100.00%> (ø)
packages/manifest/src/manifest.ts	100.00% <ø> (ø)
packages/spec-parser/src/manifestUpdater.ts	88.99% <100.00%> (ø)
packages/vscode-extension/src/codeLensProvider.ts	77.96% <100.00%> (ø)
...c/component/driver/teamsApp/utils/ManifestUtils.ts	67.02% <0.00%> (ø)