Misc TensorValue indexing improvements.

[Antoinemarteau]

I looked at MultiValue indexing in detail to address #1160.

• support for indexing with Colon()/:, end, ::StaticArray, UnitRanges, ::SOneTo, and ::Array
• support for keys
• fixed lastindex(a,d), eachindex(::IndexStyle, a)
• changed eachindex and CartesianIndices to return StaticArrays.SOneTo instead of Base.OneTo
• consistency with StaticArrays: the return value is statically typed (a scalar or MultiValue) iff all indices are statically inferable, otherwise an Array is returned.

E.g:

julia> t = TensorValue(1:9...)
TensorValue{3, 3, Int64, 9}(1, 2, 3, 4, 5, 6, 7, 8, 9)

julia> t[:,2]
VectorValue{3, Int64}(4, 5, 6)

julia> t[1:end-1,begin+1:end]
2×2 Matrix{Int64}:
 4  7
 5  8

julia> t[SOneTo(2),SOneTo(3)]
TensorValue{2, 3, Int64, 6}(1, 2, 4, 5, 7, 8)

julia> t[Base.OneTo(2),Base.OneTo(3)]
2×3 Matrix{Int64}:
 1  4  7
 2  5  8

julia> t[MVector(1,2),CartesianIndex(3)]
VectorValue{2, Int64}(7, 8)

julia> t[1:2,CartesianIndex(3)]
2-element Vector{Int64}:
 7
 8

julia> t[ isodd.(SMatrix{3,3}(1:9...))]
5-element Vector{Int64}:
 1
 3
 5
 7
 9

julia> mask = [true false false; false true false; false false true]
3×3 Matrix{Bool}:
 1  0  0
 0  1  0
 0  0  1

julia> t[mask]
3-element Vector{Int64}:
 1
 5
 9

Also, I added new constructors for MultiValue (sub)types taking SArray/MArrays and SArray/MArray's and Array's constructors taking MultiValue objects that use the existing associated convert methods. The advantage is you don't need to specify the exact size of the returned value, it's inferred from the argument

MultiValue( SMatrix{2,2}(1:4...) )  # TensorValue{2,2,Int,4}(1, 2, 3, 4)
SArray( VectorValue(1:2) ) # SVector{2,Int}(1, 2)
Array( VectorValue(1:2) ) # Int[1, 2]

but you can also specify struct arguments if you want to be sure of what you get or convert components

MVector{2,Float64}( VectorValue(1:2) ) # MVector{2,Float64}(1.0, 2.0).
Vector{Float64}( VectorValue(1:2) ) # Float64[1.0, 2.0] 

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 89.30%. Comparing base (34681f0) to head (97a2f72).
⚠️ Report is 11 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #1162      +/-   ##
==========================================
+ Coverage   89.27%   89.30%   +0.02%     
==========================================
  Files         211      211              
  Lines       26692    26710      +18     
==========================================
+ Hits        23829    23853      +24     
+ Misses       2863     2857       -6     

Flag	Coverage Δ
drivers	0.00% <0.00%> (ø)
tests	89.30% <100.00%> (+0.02%)	⬆️

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[Antoinemarteau]

This is merge-able, closes #1160.