Add bigtable and storage to conformance-tests module

[BenWhitehead]

Add test protos, test definitions and generated protos to conformance
tests module following the pattern set by firestore.

Bump conformance test to googleapis/conformance-tests@613608b

[codecov]

Codecov Report

Merging #5851 into master will increase coverage by <.01%.
The diff coverage is n/a.

@@ Coverage Diff @@## master #5851 +/- ##
============================================
+ Coverage 46.79% 46.79% +<.01% 
Complexity 25663 25663 ============================================
Files 2456 2456 Lines 267593 267593 Branches 30559 30559 ============================================
+ Hits 125228 125229 +1 + Misses 133106 133105 -1 
Partials 9259 9259

Impacted Files	Coverage Δ	Complexity Δ
...gflow/v2beta1/stub/KnowledgeBasesStubSettings.java	80.3% <0%> (ø)	15% <0%> (ø)	⬇️
...google/cloud/vision/v1/ImageAnnotatorSettings.java	17.07% <0%> (ø)	2% <0%> (ø)	⬇️
.../dialogflow/v2beta1/stub/ContextsStubSettings.java	80.57% <0%> (ø)	16% <0%> (ø)	⬇️
...stub/GameServerDeploymentsServiceStubSettings.java	88.06% <0%> (ø)	27% <0%> (ø)	⬇️
...le/cloud/gaming/v1alpha/RealmsServiceSettings.java	16.27% <0%> (ø)	2% <0%> (ø)	⬇️
...cloud/vision/v1p4beta1/ImageAnnotatorSettings.java	17.07% <0%> (ø)	2% <0%> (ø)	⬇️
...alogflow/v2beta1/stub/EntityTypesStubSettings.java	87.22% <0%> (ø)	25% <0%> (ø)	⬇️
.../v1beta1/stub/DataLabelingServiceStubSettings.java	84.42% <0%> (ø)	50% <0%> (ø)	⬇️
.../cloud/automl/v1beta1/stub/AutoMlStubSettings.java	87.6% <0%> (ø)	43% <0%> (ø)	⬇️
...loud/vision/v1/stub/ProductSearchStubSettings.java	81.87% <0%> (ø)	29% <0%> (ø)	⬇️
... and 79 more

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