CI: Use LLVM 16 tools.

[briansmith]

Rust now uses LLVM 16 and writes object files that LLVM 15's nm cannot fully understand.

[codecov]

Codecov Report

Merging #1635 (3f9cbf5) into main (95948b3) will decrease coverage by 0.04%.
Report is 2 commits behind head on main.
The diff coverage is n/a.

@@            Coverage Diff             @@
##             main    #1635      +/-   ##
==========================================
- Coverage   92.24%   92.21%   -0.04%     
==========================================
  Files         127      127              
  Lines       18811    18821      +10     
  Branches      196      196              
==========================================
+ Hits        17352    17355       +3     
- Misses       1422     1430       +8     
+ Partials       37       36       -1     

see 27 files with indirect coverage changes

📣 We’re building smart automated test selection to slash your CI/CD build times. Learn more

[briansmith]

Some CI jobs are failing due to unrelated issues. These will be resolved in separate PRs.