rustc-tests: Sort the supported tests for a more useful report

[Nadrieril]

Report after this PR:

Summary of the results:
   4845  ⊘ unsupported-build-settings
    311  ⊘ unsupported-feature
   7323  ✅ expected: failure in rustc    got: failure in rustc
   4376  ✅ expected: success             got: success (with llbc output and no warnings)
    344  ✅ expected: success             got: success (with llbc output and warnings)
     96  ❌ expected: failure in rustc    got: failure in hax frontend
    392  ❌ expected: failure in rustc    got: success
     33  ❌ expected: success             got: failure in hax frontend (without llbc output)
      8  ❌ panic
     30  ❌ stack overflow
     19  ❌ timeout

[Nadrieril]

I've sorted the unexpected failures due to hax, they're all covered by:

• Support matching on chars #546
• Support thread locals cryspen/hax#1311
• Support for promoted constants (Use a later MIR #543);
• A bunch of unhandled cases in the const conversion code.

In other words, it's all about constants except for #546.