Switch to Spotless for formatting Java code

[msridhar]

Our previous plugin for running Google Java Format was unmaintained. Also update our version of GJF, which leads to minor formatting changes.

In follow-ups, we can use Spotless to enforce formatting for .gradle files and also make license headers consistent.

[msridhar]

We can fix these incorrectly-placed license headers in a follow-up

[msridhar]

Configuring Spotless made me notice this project no longer exists in the repo

[coveralls]

Pull Request Test Coverage Report for Build #1137

• 0 of 0 changed or added relevant lines in 0 files are covered.
• 56 unchanged lines in 10 files lost coverage.
• Overall coverage remained the same at 92.808%

---

Files with Coverage Reduction	New Missed Lines	%
../nullaway/src/main/java/com/uber/nullaway/handlers/StreamNullabilityPropagatorFactory.java	1	98.04%
../nullaway/src/main/java/com/uber/nullaway/handlers/stream/StreamModelBuilder.java	3	89.13%
../nullaway/src/main/java/com/uber/nullaway/LibraryModels.java	3	88.0%
../nullaway/src/main/java/com/uber/nullaway/ErrorProneCLIFlagsConfig.java	5	94.19%
../nullaway/src/main/java/com/uber/nullaway/fixserialization/FixSerializationConfig.java	5	90.48%
../nullaway/src/main/java/com/uber/nullaway/fixserialization/out/SuggestedNullableFixInfo.java	5	50.0%
../nullaway/src/main/java/com/uber/nullaway/handlers/AbstractFieldContractHandler.java	5	90.16%
../nullaway/src/main/java/com/uber/nullaway/dataflow/AccessPath.java	6	96.84%
../nullaway/src/main/java/com/uber/nullaway/dataflow/NullnessStore.java	9	88.16%
../nullaway/src/main/java/com/uber/nullaway/fixserialization/Serializer.java	14	81.58%

Totals
Change from base Build #1134:	0.0%
Covered Lines:	5613
Relevant Lines:	6048

---

💛 - Coveralls

[ketkarameya]

LGTM.