fix type instability of restrict

[johnnychen94]

There're two type instabilities come up in the recent upstream update:

• The first is due to similar improvement on OffsetArray (new type instability during restrict on OffsetArray #118) and nicely fixed with the patch provided by @jishnub
• The second is due to the recent (I believe) Colors update (the root is not identified). This is fixed by rewriting the raestrict_eltype implementation without doing runtime calculation (as possible as we can).

closes #118

[codecov]

Codecov Report

Merging #124 (28e612f) into master (a476cee) will increase coverage by 0.26%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master     #124      +/-   ##
==========================================
+ Coverage   94.76%   95.02%   +0.26%     
==========================================
  Files           7        7              
  Lines         363      362       -1     
==========================================
  Hits          344      344              
+ Misses         19       18       -1     

Impacted Files	Coverage Δ
src/resizing.jl	98.78% <100.00%> (+0.59%)	⬆️

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