Combine build and test GHA steps.
Combine build and test GHA steps.

There's no particular reason to separate them, and merging them will allow bazel to better parallelize its actions.

PiperOrigin-RevId: 334819388

ChadKillingsworth/closure-compiler,monetate/closure-compiler,google/closure-compiler,google/closure-compiler,google/closure-compiler,Yannic/closure-compiler,nawawi/closure-compiler,monetate/closure-compiler,vobruba-martin/closure-compiler,vobruba-martin/closure-compiler,monetate/closure-compiler,Yannic/closure-compiler,ChadKillingsworth/closure-compiler,nawawi/closure-compiler,vobruba-martin/closure-compiler,ChadKillingsworth/closure-compiler,monetate/closure-compiler,vobruba-martin/closure-compiler,Yannic/closure-compiler,nawawi/closure-compiler,nawawi/closure-compiler,google/closure-compiler,ChadKillingsworth/closure-compiler,Yannic/closure-compiler