Add testgen CLI to generate moon ide cram tests

[bzy-debug]

This PR adds a moonbit CLI testgen to generate moon ide subcommand cram tests of a moonbit project.

Given a moonbit project, testgen will generate following files:

├── dune # a dune file to enable cram tests in current folder
├── generated_find_references.t # tests of moon ide find-references
├── generated_hover.t # tests of moon ide hover
├── generated_outline.t # tests of moon ide outline
├── generated_peek_def.t # tests of moon ide peek-def
├── generated_rename.t # tests of moon ide rename

testgen uses moonbitlang/parser to parse every moonbit file, collect all testable localtions from ast nodes (lident, uident, dot_ident, etc.), then output serveral .t files for testing.

The generated tests also finds the bug that's already revealed by 52afcd1:

  $ moon ide hover Item --loc sample.mbt:3:10
  No hover information found for symbol 'Item' at sample.mbt:3:10
  [1]

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[bzy-debug]

@codex review

[bzy-debug]

@codex review

[bzy-debug]

@codex review

[devin-ai-integration]

✅ Devin Review: No Issues Found

Devin Review analyzed this PR and found no potential bugs to report.

View in Devin Review to see 6 additional findings.