Refactor [g]crane to make threading options easier

[jonjohnsonjr]

I've split out some of this from #837

This addresses a few things:

1. gcrane now inherits the options/flags from crane (e.g. --insecure, --platform, -v, the headerTransport thing). Some of these were duplicated code, others were just broken in gcrane.
2. Drop most use of init for the cmd packages
3. Allow passing in a keychain or auth to crane (Fixes Adds WithAuth functional option to pkg/crane to allow for alternate m… #653).
4. Create and thread gcrane.Keychain through as the default keychain for gcrane (Fixes Use Google keychain on gcrane commands #721).

I ended up passing a pointer to a slice of options through the command init logic, which feels kind of gross, but a lot less gross than having package-level globals... let me know if you have a better suggestion. I think we need to do this because PersistentPreRun has to modify the options, but we've already created each command by the time that runs... :/

[codecov-io]

Codecov Report

Merging #845 (7d765ad) into master (93b58dc) will decrease coverage by 0.17%.
The diff coverage is 50.00%.

@@            Coverage Diff             @@
##           master     #845      +/-   ##
==========================================
- Coverage   74.77%   74.59%   -0.18%     
==========================================
  Files         106      106              
  Lines        4420     4421       +1     
==========================================
- Hits         3305     3298       -7     
- Misses        626      633       +7     
- Partials      489      490       +1     

Impacted Files	Coverage Δ
pkg/crane/options.go	52.94% <0.00%> (-16.29%)	⬇️
pkg/gcrane/copy.go	84.37% <75.00%> (-1.14%)	⬇️
pkg/v1/tarball/write.go	61.45% <0.00%> (-0.98%)	⬇️
pkg/v1/remote/image.go	79.45% <0.00%> (+0.28%)	⬆️

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