stats: expose non-cacheable Rust crate types

[codeandsolder]

Summary

Rust's argument parser already attaches the specific non-cacheable crate type to CompilerArguments::CannotCache("crate-type", ...), but server statistics discard that detail and record every case as crate-type.

Keep the existing not_cached statistics map and include the detail in its key for this reason, for example crate-type (bin) and crate-type (proc-macro). Other non-cacheable reasons are unchanged.

When rustc supplies multiple unsupported crate types, sort them before recording the detail so the statistic key is deterministic regardless of input order.

This avoids adding a new serialized statistics field or otherwise changing the statistics schema.

Testing

• cargo +1.99.0 fmt --all -- --check
• cargo +1.99.0 test --locked --no-default-features --lib non_cacheable_crate_type
• cargo +1.99.0 test --locked --no-default-features --lib test_print_non_cacheable_crate_type_details
• Rust 1.99 through sccache

AI Disclosure: AI developed, human directed and reviewed

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 78.23%. Comparing base (81c2834) to head (f340de5).
⚠️ Report is 5 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #2897      +/-   ##
==========================================
+ Coverage   78.18%   78.23%   +0.05%     
==========================================
  Files          72       72              
  Lines       41946    42048     +102     
==========================================
+ Hits        32795    32897     +102     
  Misses       9151     9151              

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