refactor!: separate SDK and Parser

[KyleTryon]

This PR removes the parsing functionality of the Config SDK and relocates the logic to a separate package named @circleci/circleci-config-parser, which will have the SDK as a dependency

Why?

1. Remove a large amount of code that will not be used by the majority of developers attempting to generate configs for CI
2. Removes external dependencies on AJV and related libraries used for schema checking
3. Prepares the library for potential JSII integration

Other:

This PR contains a large number of commits and changes. The following explains the reasoning:

• Split the "parsing" source into a separate package
• Manage the two "sdk" and "parser" packages as a mono repo with Lerna
  • This was useful for development in the interim but ultimately proved challenging for deployments if kept long term.
• Refactor several changes while the code bases are still together
  • change types.executor to types.executors to match the components
  • change Config.generate to output JSON like the other generate functions
  • add the stringify function to Config to "replace" the generate function to produce the stringified YAML
  • change asReusable on Executor to toReusable
  • add ReusedCommand
  • add toReused to ReusableCommand
  • improve some documentation
  • drop support for Node v12 (unsupported)
  • update dependencies and resolve all security alerts

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Legend

[codecov[bot]]

Codecov Report

Merging #114 (6af09e7) into main (48bff2c) will decrease coverage by 0.32%. The diff coverage is 98.41%.

@@             Coverage Diff             @@
##              main     #114      +/-   ##
===========================================
- Coverage   100.00%   99.67%   -0.33%     
===========================================
  Files          106       61      -45     
  Lines         1025      614     -411     
  Branches        87       46      -41     
===========================================
- Hits          1025      612     -413     
- Misses           0        1       +1     
- Partials         0        1       +1     

Impacted Files	Coverage Δ
...b/Components/Commands/exports/Native/AddSSHKeys.ts	100.00% <ø> (ø)
...omponents/Commands/exports/Native/Cache/Restore.ts	100.00% <ø> (ø)
...b/Components/Commands/exports/Native/Cache/Save.ts	100.00% <ø> (ø)
...lib/Components/Commands/exports/Native/Checkout.ts	100.00% <ø> (ø)
...nents/Commands/exports/Native/SetupRemoteDocker.ts	100.00% <ø> (ø)
...mponents/Commands/exports/Native/StoreArtifacts.ts	100.00% <ø> (ø)
...onents/Commands/exports/Native/StoreTestResults.ts	100.00% <ø> (ø)
...onents/Commands/exports/Native/Workspace/Attach.ts	100.00% <ø> (ø)
...nents/Commands/exports/Native/Workspace/Persist.ts	100.00% <ø> (ø)
...rc/lib/Components/Executors/exports/DockerImage.ts	100.00% <ø> (ø)
... and 23 more

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