Add `redirect_stdio` (feature from `v1.7`)

[MilesCranmer]

From https://github.com/JuliaLang/julia/pull/37978. This completely copies the code from that PR, with one fix for samefile -> Base.Filesystem.samefile. Unit tests are copied as well.

[codecov[bot]]

Codecov Report

Merging #801 (3ce84cb) into master (70ab162) will increase coverage by 0.84%. The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master     #801      +/-   ##
==========================================
+ Coverage   91.69%   92.54%   +0.84%     
==========================================
  Files           2        2              
  Lines         265      295      +30     
==========================================
+ Hits          243      273      +30     
  Misses         22       22              

Impacted Files	Coverage Δ
src/Compat.jl	93.06% <100.00%> (+0.85%)	:arrow_up:

[MilesCranmer]

Actually wait, I'm being an idiot. I should have just copied it in verbatim – the other functionality added has no effect on existing redirection.

[MilesCranmer]

Updated. Now it's a full copy of the code with everything working.

[MilesCranmer]

Done!