make StaticArrays dependency into an extension on v0.11-dev

[ChrisRackauckas]

Rebased version of #617. Matches the code of #625

[ Edit: merging this closes#599, closes#617 ]

[codecov-commenter]

Codecov Report

Base: 89.76% // Head: 87.28% // Decreases project coverage by -2.49%⚠️

Coverage data is based on head (df7e6e0) compared to base (4b143a1).
Patch coverage: 98.83% of modified lines in pull request are covered.

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Additional details and impacted files

@@ Coverage Diff @@## master #628 +/- ##
==========================================
- Coverage 89.76% 87.28% -2.49% 
==========================================
Files 10 10 Lines 967 912 -55 ==========================================
- Hits 868 796 -72 - Misses 99 116 +17 

Impacted Files	Coverage Δ
src/apiutils.jl	100.00% <ø> (ø)
src/dual.jl	80.30% <ø> (-2.48%)	⬇️
src/gradient.jl	98.66% <ø> (-0.29%)	⬇️
src/hessian.jl	100.00% <ø> (+2.43%)	⬆️
src/jacobian.jl	99.15% <ø> (-0.19%)	⬇️
ext/ForwardDiffStaticArraysExt.jl	98.83% <98.83%> (ø)
src/prelude.jl	36.36% <0.00%> (-57.58%)	⬇️
... and 1 more

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[ChrisRackauckas]

No objections from anyone? Speak up by Friday?

[ChrisRackauckas]

Same as #625 (comment) , the failure is only on nightly and not v1.9-beta3, and it's the same failure on master according to #626, so it's a nightly issue and unrelated. Merging so that the release and master branches are synced.