Create new google-cloud-conformance-tests module

[BenWhitehead]

A new module where common code related to conformance tests can be
shared.

• Includes a rudimentary classpath scanner that can be used to locate
  test definitions. (The firestore test suite currently have 224 test
  definitions.)
  • The classpath scanner includes a suite of tests to ensure it can
    accurately find resources in jar files and directories.
  • Tests have been ran against the following JVMs on Linux x64 and
    verified to pass.

    openjdk version "1.7.0_75"
    OpenJDK Runtime Environment (build 1.7.0_75-b13)
    OpenJDK 64-Bit Server VM (build 24.75-b04, mixed mode)
    java version "1.8.0_201"
    Java(TM) SE Runtime Environment (build 1.8.0_201-b09)
    Java HotSpot(TM) 64-Bit Server VM (build 25.201-b09, mixed mode)
    java version "11.0.2" 2019-01-15 LTS
    Java(TM) SE Runtime Environment 18.9 (build 11.0.2+9-LTS)
    Java HotSpot(TM) 64-Bit Server VM 18.9 (build 11.0.2+9-LTS, mixed mode)
    openjdk version "12" 2019-03-19
    OpenJDK Runtime Environment (build 12+33)
    OpenJDK 64-Bit Server VM (build 12+33, mixed mode, sharing)
    

[BenWhitehead]

Replacing #5537

[BenWhitehead]

@kolea2 Please review

[kolea2]

Looks ok to me, adding in @chingor13 for a core perspective.

[codecov]

Codecov Report

Merging #5540 into master will increase coverage by 0.32%.
The diff coverage is n/a.

@@ Coverage Diff @@## master #5540 +/- ##
============================================
+ Coverage 46.39% 46.71% +0.32% 
Complexity 24645 24645 ============================================
Files 2351 2351 Lines 256176 256176 Branches 29294 29319 +25 ============================================
+ Hits 118853 119683 +830 + Misses 127611 127573 -38 + Partials 9712 8920 -792

Impacted Files	Coverage Δ	Complexity Δ
...gle/cloud/storage/testing/RemoteStorageHelper.java	62.6% <0%> (-2.44%)	9% <0%> (ø)
...m/google/cloud/bigquery/QueryJobConfiguration.java	75.15% <0%> (+0.31%)	50% <0%> (ø)	⬇️
...om/google/cloud/bigquery/LoadJobConfiguration.java	88.73% <0%> (+0.45%)	46% <0%> (ø)	⬇️
...ogle/cloud/bigquery/WriteChannelConfiguration.java	86.12% <0%> (+0.47%)	44% <0%> (ø)	⬇️
...java/com/google/cloud/firestore/FirestoreImpl.java	83.42% <0%> (+0.57%)	22% <0%> (ø)	⬇️
...main/java/com/google/cloud/storage/BucketInfo.java	84.6% <0%> (+0.58%)	78% <0%> (ø)	⬇️
...n/java/com/google/cloud/bigquery/BigQueryImpl.java	80% <0%> (+0.63%)	57% <0%> (ø)	⬇️
.../com/google/cloud/compute/deprecated/DiskInfo.java	96.5% <0%> (+0.69%)	29% <0%> (ø)	⬇️
...om/google/cloud/notification/NotificationInfo.java	90% <0%> (+1%)	26% <0%> (ø)	⬇️
.../cloud/scheduler/v1beta1/CloudSchedulerClient.java	55% <0%> (+1%)	35% <0%> (ø)	⬇️
... and 135 more

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[BenWhitehead]

@chingor13 Requests integrated. Failing windows build appears to be the spanner test that is flaky on windows.

[BenWhitehead]

Thanks for merging @chingor13!