feat(cli): add internal `_generate` and `_build` flags

[pi0]

Types of changes

• Bug fix (a non-breaking change which fixes an issue)
• New feature (a non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)

Description

Previously we had internal flag options._start, this PR also adds options._build and options._generate when running CLI commands so 1) options.js 2) modules can predict if a builder or generator is supposed to be started with the current instance. (Useful for #5354.)

Checklist:

• My change requires a change to the documentation.
• I have updated the documentation accordingly. (PR: #)
• I have added tests to cover my changes (if not applicable, please state why)
• All new and existing tests are passing.

[codecov-io]

Codecov Report

Merging #5434 into dev will decrease coverage by 0.03%.
The diff coverage is 100%.

@@            Coverage Diff             @@
##              dev    #5434      +/-   ##
==========================================
- Coverage   96.16%   96.12%   -0.04%     
==========================================
  Files          74       74              
  Lines        2555     2555              
  Branches      650      650              
==========================================
- Hits         2457     2456       -1     
- Misses         82       83       +1     
  Partials       16       16

Impacted Files	Coverage Δ
packages/cli/src/commands/generate.js	91.3% <100%> (ø)	⬆️
packages/cli/src/commands/build.js	86.36% <100%> (ø)	⬆️
packages/cli/src/commands/dev.js	84.61% <100%> (ø)	⬆️
packages/vue-renderer/src/renderer.js	95.56% <0%> (-0.5%)	⬇️

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