Make root build.gradle easier to read:
- Moved appengine war-assembly into separate script
- Moved java static analysis configs to separate script,
for easier sharing with buildSrc folder.
Update Gradle config in the buildSrc folder:
- Applied static analysis, and cleaned up a few style and
dependency lint errors.
- Added dependency locks
- Set up Google java format enforcement (Spotless)
since this is new code.
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Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=246858172
