Bump MSRV from 1.88.0 to 1.94.0

[Jefffrey]

see previous bump

• Bump MSRV to 1.88.0 #18403

honestly my main motivation was i was using a feature from 1.89.0 apparently for #23631 and realized we hadn't bumped this in a while

if we prefer to be more conservative with msrv bumps (i.e. only bump if a dependency requires it or we see a really useful feature/lib function in newer versions) then i'm fine with leaving it and altering my PR above, but in the past we usually kept up to date with bumping our msrv

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 80.71%. Comparing base (0de74cc) to head (f2a7139).
⚠️ Report is 3 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #23632      +/-   ##
==========================================
- Coverage   80.71%   80.71%   -0.01%     
==========================================
  Files        1089     1089              
  Lines      368911   368911              
  Branches   368911   368911              
==========================================
- Hits       297783   297769      -14     
- Misses      53373    53385      +12     
- Partials    17755    17757       +2     

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[neilconway]

Personally I'm okay with bumping MSRV more aggressively, but I don't know if we have a policy on it.

[pepijnve]

On discord @Omega359 pointed to https://datafusion.apache.org/user-guide/introduction.html#rust-version-compatibility-policy. Since we're at Rust 1.97, bumping to 1.94 would be in line with the policy of supporting the last 4 stable releases.

[neilconway]

If that's the policy, I'm fine with landing this now -- let me know if anyone feels otherwise.

@Jefffrey Can you resolve the merge conflict when you get a chance?