Update Error Prone's tests to use 4 forks and reuse forks to speed up execution on machines with more CPU's.
Update Error Prone's tests to use 4 forks and reuse forks to speed up execution on machines with more CPU's.

RELNOTES: n/a

GOOGLE: And use the shared maven_test script to avoid duplicate code

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Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=257524161

google/error-prone,cushon/error-prone,google/error-prone,cushon/error-prone,cushon/error-prone,cushon/error-prone