refactor: remove feature flags

[tecton]

Removed feature flags: BUILDER API, isKiotaIntegration, OfficeMetaOS, ChatParticipant

[codecov]

Codecov Report

❌ Patch coverage is 94.59459% with 2 lines in your changes missing coverage. Please review.
✅ Project coverage is 89.31%. Comparing base (5572a82) to head (5d18e6f).
⚠️ Report is 16 commits behind head on dev.

Files with missing lines	Patch %	Lines
packages/fx-core/src/core/FxCore.ts	89.47%	1 Missing and 1 partial ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##              dev   #15043      +/-   ##
==========================================
- Coverage   89.46%   89.31%   -0.15%     
==========================================
  Files         606      606              
  Lines       37239    37165      -74     
  Branches     7465     7591     +126     
==========================================
- Hits        33315    33194     -121     
- Misses       1837     1893      +56     
+ Partials     2087     2078       -9     

Files with missing lines	Coverage Δ
packages/fx-core/src/common/featureFlags.ts	96.49% <ø> (-0.44%)	⬇️
...ackages/fx-core/src/component/coordinator/index.ts	86.27% <100.00%> (-0.17%)	⬇️
...core/src/component/generator/openApiSpec/common.ts	93.61% <100.00%> (-0.51%)	⬇️
...-core/src/component/generator/openApiSpec/kiota.ts	14.28% <ø> (-79.27%)	⬇️
...kages/fx-core/src/component/m365/packageService.ts	92.05% <100.00%> (-0.07%)	⬇️
packages/fx-core/src/question/other.ts	91.35% <ø> (ø)
...re/src/question/scaffold/vsc/ProjectTypeOptions.ts	100.00% <100.00%> (ø)
...x-core/src/question/scaffold/vsc/createRootNode.ts	94.00% <100.00%> (+1.69%)	⬆️
...ore/src/question/scaffold/vsc/daProjectTypeNode.ts	100.00% <100.00%> (ø)
...uestion/scaffold/vsc/officeAddinProjectTypeNode.ts	100.00% <100.00%> (ø)
... and 1 more

... and 6 files with indirect coverage changes

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