Preserve axes in permutedims

[jishnub]

The vector method is unnecessary, as the fallback Base method uses reshape, which will do the same.

For the other method:
On master,

julia> F = Fill(2, (SOneTo(2), SOneTo(3)))
2×3 Fill{Int64, 2, Tuple{SOneTo{2}, SOneTo{3}}} with indices SOneTo(2)×SOneTo(3), with entries equal to 2

julia> permutedims(F)
3×2 Fill{Int64, 2, Tuple{SOneTo{3}, SOneTo{2}}} with indices SOneTo(3)×SOneTo(2), with entries equal to 2

julia> permutedims(F, (2,1))
3×2 Fill{Int64}, with entries equal to 2

In the second operation, the static axes are lost. After this PR, the axes are preserved:

julia> permutedims(F, (2,1))
3×2 Fill{Int64, 2, Tuple{SOneTo{3}, SOneTo{2}}} with indices SOneTo(3)×SOneTo(2), with entries equal to 2

To make this type-stable, we require aggressive constant propagation on the permutation tuple.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (c7c34aa) 99.89% compared to head (7ce8f5b) 99.89%.

Additional details and impacted files

@@           Coverage Diff           @@
##           master     #319   +/-   ##
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  Coverage   99.89%   99.89%           
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  Files           8        8           
  Lines         920      921    +1     
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+ Hits          919      920    +1     
  Misses          1        1           

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