Write TF proto results using size-delimited format

Configure Tradefed to write size-delimited proto result files. This is
required because the BazelTest driver parses these size-delimited
records.

Test: atest bazel-test-runner-tests
Bug: 262916831
Change-Id: I2f8a82f3e6e17af6a728aee915b697b2de72f778
1 file changed