CI: update to clang 16 and llvm 16

[pheiduck]

No description provided.

[codecov]

Codecov Report

Merging #11577 (33933bc) into master (7a1bdae) will increase coverage by 0.00%.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master   #11577   +/-   ##
=======================================
  Coverage   81.90%   81.91%           
=======================================
  Files         164      164           
  Lines      193675   193675           
  Branches    43787    43787           
=======================================
+ Hits       158634   158640    +6     
+ Misses      22215    22206    -9     
- Partials    12826    12829    +3     

Flag	Coverage Δ
huge-clang-none	82.62% <ø> (ø)
huge-gcc-none	53.46% <ø> (ø)
huge-gcc-testgui	51.57% <ø> (ø)
huge-gcc-unittests	0.29% <ø> (ø)
linux	82.33% <ø> (-0.01%)	⬇️
mingw-x64-HUGE	76.48% <ø> (-0.01%)	⬇️
mingw-x86-HUGE	76.95% <ø> (+<0.01%)	⬆️
windows	78.08% <ø> (+<0.01%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
src/spellfile.c	80.36% <0.00%> (-0.14%)	⬇️
src/gui_gtk_x11.c	51.73% <0.00%> (-0.10%)	⬇️
src/search.c	85.11% <0.00%> (-0.09%)	⬇️
src/gui.c	72.67% <0.00%> (ø)
src/channel.c	83.05% <0.00%> (ø)
src/regexp_nfa.c	89.70% <0.00%> (+0.03%)	⬆️
src/terminal.c	77.87% <0.00%> (+0.05%)	⬆️
src/netbeans.c	72.17% <0.00%> (+0.07%)	⬆️
src/gui_w32.c	39.81% <0.00%> (+0.17%)	⬆️
src/if_xcmdsrv.c	77.98% <0.00%> (+0.34%)	⬆️
... and 1 more

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[pheiduck]

@brammool this can be merged.