Get rid of Ramble's dependency on spack_json

[linsword13]

Instead, implement thin helpers under ramble.util.

[gemini-code-assist]

Code Review

This pull request replaces the vendored spack.util.spack_json dependency with a new internal ramble.util.json_util module across the codebase, updating all references, adding unit tests, and enforcing this change via Ruff in pyproject.toml. Feedback suggests explicitly typing dump_args as Dict[str, Any] in json_util.py to improve type safety and remove the need for # type: ignore comments.

[linsword13]

/gemini review

[gemini-code-assist]

Code Review

This pull request replaces the dependency on spack.util.spack_json with a new internal utility ramble.util.json_util across the codebase, enforcing this restriction via pyproject.toml. However, the new utility lacks a custom serialization handler for types like set, Enum, and objects with to_dict methods, which were previously supported by spack_json. This regression could lead to runtime serialization errors and non-deterministic hashing. It is recommended to implement a custom default handler in json_util and add corresponding unit tests to verify correct behavior.

[ramble-pr-bot]

Ramble Performance Test Metrics

Results produced with commit: fbe9cb4

Test Name	Outcome	Duration (s)	Most Recent Run (s)	Last 5 Avg (s)
test_analyze_large_file	passed	2.9109	2.9405 (1ebc534)	2.9284
test_large_template_expansion	passed	2.1264	2.1471 (1ebc534)	2.1558
test_many_experiments	passed	37.5218	36.5583 (1ebc534)	37.7597
test_many_objects_defaults	passed	20.3769	19.4925 (1ebc534)	20.1742
test_matrix_filter_perf	passed	1.6112	1.5775 (1ebc534)	1.6123

[codecov]

Codecov Report

❌ Patch coverage is 93.58974% with 5 lines in your changes missing coverage. Please review.
✅ Project coverage is 93.30%. Comparing base (1ebc534) to head (fbe9cb4).

Files with missing lines	Patch %	Lines
lib/ramble/ramble/mirror.py	20.00%	4 Missing ⚠️
lib/ramble/ramble/repository.py	66.66%	1 Missing ⚠️

Additional details and impacted files

@@           Coverage Diff            @@
##           develop    #1648   +/-   ##
========================================
  Coverage    93.30%   93.30%           
========================================
  Files          352      354    +2     
  Lines        34223    34256   +33     
========================================
+ Hits         31931    31964   +33     
  Misses        2292     2292           

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