Add isomorphism(::Type{PermGroup}, ::WeylGroup) for some cases

[lgoettgens]

This PR contains the changes from #4260 in experimental/LieAlgebras, makes them a bit more consistent with the surrounding code, and adds tests.

[codecov]

Codecov Report

Attention: Patch coverage is 89.28571% with 3 lines in your changes missing coverage. Please review.

Project coverage is 84.60%. Comparing base (852b6d1) to head (2286d23).
Report is 5 commits behind head on master.

Files with missing lines	Patch %	Lines
experimental/LieAlgebras/src/WeylGroup.jl	89.28%	3 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #4264      +/-   ##
==========================================
- Coverage   84.60%   84.60%   -0.01%     
==========================================
  Files         640      640              
  Lines       85128    85145      +17     
==========================================
+ Hits        72021    72034      +13     
- Misses      13107    13111       +4     

Files with missing lines	Coverage Δ
experimental/LieAlgebras/src/LieAlgebras.jl	100.00% <ø> (ø)
experimental/LieAlgebras/test/WeylGroup-test.jl	97.77% <ø> (ø)
experimental/LieAlgebras/src/WeylGroup.jl	92.03% <89.28%> (-0.25%)	⬇️

... and 3 files with indirect coverage changes