Add WithContext to google.ListerOption

[micnncim]

Added WithContext function, which implements google.ListerOption. This enables us to pass context.Context so that we could cancel sending HTTP requests. This PR won't change the default behavior since (*http.Client).Get wraps http.NewRequest and (*http.Client).Do and http.NewRequest wraps http.NewRequestWithContext with context.Background.

[codecov-commenter]

Codecov Report

Merging #776 into master will decrease coverage by 0.08%.
The diff coverage is 37.50%.

@@            Coverage Diff             @@
##           master     #776      +/-   ##
==========================================
- Coverage   75.99%   75.91%   -0.09%     
==========================================
  Files         102      102              
  Lines        4132     4139       +7     
==========================================
+ Hits         3140     3142       +2     
- Misses        542      546       +4     
- Partials      450      451       +1     

Impacted Files	Coverage Δ
pkg/v1/google/options.go	70.58% <0.00%> (-15.13%)	⬇️
pkg/v1/google/list.go	62.06% <60.00%> (-0.59%)	⬇️

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[jonjohnsonjr]

Looks great, thanks!

Sorry for the delay, I've been away on vacation.