Add nimbus-fml command for info

[jhugman]

Relates to EXP-3938.

According to The Big O of Code Reviews, this is a O(n) change.

This PR is the final piece in EXP-3938, adding per-feature hashes to the FML.

We end here with an info command to add to the nimbus-fml command line. It outputs JSON / YAML with a summmary of each feature including:

• the types used, as a proxy for feature complexity
• feature metadata, including documentation and events
• the schema hash and defaults hash.

The PRs to get here are:

• Tidy intermediate_representation tests Part I #5938
• Move structure validation to separate structure validator #5939
• Rewrite serde_json::Value as serde_json::json #5946
• Rationalize PropDef, EnumDef and EnumDef test constructors #5947
• Add a structure hash to FeatureInspector #5949
• Rename structure --> schema #5959
• Add defaults_hash and tests #5962

The final PR (this one):

• Add nimbus-fml command for info #5967

Pull Request checklist

• Breaking changes: This PR follows our breaking change policy
  • This PR follows the breaking change policy:
    • This PR has no breaking API changes, or
    • There are corresponding PRs for our consumer applications that resolve the breaking changes and have been approved
• Quality: This PR builds and tests run cleanly
  • Note:
    • For changes that need extra cross-platform testing, consider adding [ci full] to the PR title.
    • If this pull request includes a breaking change, consider cutting a new release after merging.
• Tests: This PR includes thorough tests or an explanation of why it does not
• Changelog: This PR includes a changelog entry in CHANGELOG.md or an explanation of why it does not need one
  • Any breaking changes to Swift or Kotlin binding APIs are noted explicitly
• Dependencies: This PR follows our dependency management guidelines
  • Any new dependencies are accompanied by a summary of the due dilligence applied in selecting them.

Branch builds: add [firefox-android: branch-name] to the PR title.

[codecov-commenter]

Codecov Report

Attention: 62 lines in your changes are missing coverage. Please review.

Comparison is base (6581e46) 27.64% compared to head (b40ec3b) 27.65%.
Report is 2 commits behind head on main.

Files	Patch %	Lines
components/support/nimbus-fml/src/backends/info.rs	0.00%	41 Missing ⚠️
...s/support/nimbus-fml/src/command_line/workflows.rs	0.00%	12 Missing ⚠️
...ponents/support/nimbus-fml/src/command_line/mod.rs	83.78%	6 Missing ⚠️
...port/nimbus-fml/src/intermediate_representation.rs	0.00%	3 Missing ⚠️

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #5967   +/-   ##
=======================================
  Coverage   27.64%   27.65%           
=======================================
  Files         380      381    +1     
  Lines       48356    48447   +91     
=======================================
+ Hits        13370    13400   +30     
- Misses      34986    35047   +61     

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

[jeddai]

Looks good!