Add a preference system for turning on/off slow fallbacks

[ChrisRackauckas]

This gives a good way to balance development vs usage. For development, you want to just error if you hit any slower path. But for users, code should just work. Thus the slower fallbacks were given a preference system for allowing error throwing, without forcing all users to have to always see errors on new types just for more optimizations.

[codecov[bot]]

Codecov Report

Merging #402 (4258a60) into master (e1870b7) will decrease coverage by 75.32%. The diff coverage is 0.00%.

@@            Coverage Diff             @@
##           master    #402       +/-   ##
==========================================
- Coverage   75.31%   0.00%   -75.32%     
==========================================
  Files           7       7               
  Lines         563     550       -13     
==========================================
- Hits          424       0      -424     
- Misses        139     550      +411     

Impacted Files	Coverage Δ
src/ArrayInterface.jl	0.00% <0.00%> (-74.40%)	:arrow_down:

... and 4 files with indirect coverage changes

:mega: We’re building smart automated test selection to slash your CI/CD build times. Learn more