LieAlgebras: Enhance module interface

[lgoettgens]

Currently, there is some weird behavior when two identical modules have been constructed in different ways, e.g. some module and its 1st exterior power.

julia> L = special_orthogonal_lie_algebra(QQ, 4)
LinearLieAlgebra (⊆ gl_4) over Rational Field

julia> std_V = standard_module(L)
StdModule of LinearLieAlgebra (⊆ gl_4) over Rational Field

julia> V = exterior_power(std_V, 1)
<StackOverflowError>

julia> is_exterior_power(std_V)
true

This PR first adds tests modeling the intended behavior and then approaches to fix the above accordingly.

While on my way, I may add some more module constructions.

[codecov]

Codecov Report

Merging #2262 (309aff2) into master (ef38ade) will increase coverage by 0.09%.
The diff coverage is 88.81%.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #2262      +/-   ##
==========================================
+ Coverage   73.47%   73.57%   +0.09%     
==========================================
  Files         367      367              
  Lines       50277    50384     +107     
==========================================
+ Hits        36940    37068     +128     
+ Misses      13337    13316      -21     

Impacted Files	Coverage Δ
experimental/LieAlgebras/src/AbstractLieAlgebra.jl	82.92% <ø> (+2.43%)	⬆️
...rimental/LieAlgebras/test/LinearLieAlgebra-test.jl	87.50% <ø> (ø)
...rimental/LieAlgebras/test/LieAlgebraModule-test.jl	89.87% <75.00%> (-0.67%)	⬇️
experimental/LieAlgebras/test/LieAlgebra-test.jl	91.30% <80.00%> (+0.25%)	⬆️
experimental/LieAlgebras/src/LieAlgebra.jl	84.46% <88.88%> (-0.39%)	⬇️
experimental/LieAlgebras/src/LieAlgebraModule.jl	85.89% <89.78%> (+5.28%)	⬆️
experimental/LieAlgebras/src/GapWrapper.jl	94.59% <100.00%> (ø)
...mental/LieAlgebras/test/AbstractLieAlgebra-test.jl	100.00% <100.00%> (ø)

... and 14 files with indirect coverage changes

[lgoettgens]

Here, I changed it from an abstract Tuple{Vararg{LieAlgebraModule{C}}} to a concrete Vector{LieAlgebraModule{C}}. @fingolfin

[lgoettgens]

This is ready for review and merge now. Since I expect some small conflict with #2207, I would rather merge this one first and deal with #2207 later. I anticipate a discussion or at least some ugly hacks there.

[fingolfin]

Fine by me