Remove backoffutils and added the files to retry package

[yashrsharma44]

Fixes #388

[bwplotka]

Sweet! Thank you! LGTM, just minor nit.

[codecov-io]

Codecov Report

Merging #390 (825f32f) into v2 (a79558a) will decrease coverage by 27.83%.
The diff coverage is 37.59%.

@@             Coverage Diff             @@
##               v2     #390       +/-   ##
===========================================
- Coverage   83.58%   55.74%   -27.84%     
===========================================
  Files          30       36        +6     
  Lines         932     1322      +390     
===========================================
- Hits          779      737       -42     
- Misses        114      514      +400     
- Partials       39       71       +32     

Impacted Files	Coverage Δ
chain.go	0.00% <ø> (-90.91%)	⬇️
interceptors/auth/auth.go	100.00% <ø> (ø)
interceptors/auth/metadata.go	100.00% <ø> (ø)
interceptors/ratelimit/ratelimit.go	50.00% <0.00%> (-50.00%)	⬇️
interceptors/tags/fieldextractor.go	13.79% <0.00%> (-71.51%)	⬇️
testing/testpb/interceptor_suite.go	0.00% <0.00%> (ø)
testing/testpb/test.manual_extractfields.pb.go	0.00% <0.00%> (ø)
testing/testpb/test.manual_validator.pb.go	0.00% <0.00%> (ø)
testing/testpb/test.pb.go	36.92% <36.92%> (ø)
interceptors/logging/payload.go	67.18% <42.30%> (-15.43%)	⬇️
... and 45 more

---

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[yashrsharma44]

Can we get this merged? cc @bwplotka

[codecov-commenter]

Codecov Report

Merging #390 (f378920) into v2 (6e2c2ac) will decrease coverage by 26.06%.
The diff coverage is 42.69%.

❗ Current head f378920 differs from pull request most recent head 4873611. Consider uploading reports for the commit 4873611 to get more accurate results

@@             Coverage Diff             @@
##               v2     #390       +/-   ##
===========================================
- Coverage   84.01%   57.94%   -26.07%     
===========================================
  Files          30       38        +8     
  Lines         932     1674      +742     
===========================================
+ Hits          783      970      +187     
- Misses        110      632      +522     
- Partials       39       72       +33     

Impacted Files	Coverage Δ
chain.go	0.00% <ø> (-90.91%)	⬇️
interceptors/auth/auth.go	100.00% <ø> (ø)
interceptors/auth/metadata.go	100.00% <ø> (ø)
interceptors/logging/options.go	82.85% <0.00%> (-7.77%)	⬇️
interceptors/ratelimit/ratelimit.go	60.00% <0.00%> (-40.00%)	⬇️
interceptors/recovery/options.go	78.57% <ø> (ø)
interceptors/tags/context.go	64.00% <ø> (ø)
interceptors/tags/fieldextractor.go	15.15% <0.00%> (-70.15%)	⬇️
interceptors/tags/interceptors.go	95.65% <ø> (ø)
interceptors/tags/options.go	100.00% <ø> (ø)
... and 42 more

---

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[johanbrandhorst]

LGTM, small suggestion about the new methods.