Report action executions errors through `ExecuteResponse` about bazel-buildfarm HOT 3 CLOSED

What needs to be verified, probably already there:

• when the execution times out, a DEADLINE_EXCEEDED status should be returned in the ExecuteResponse status field. It should never be returned as the gRPC status, because that means a different thing semantically.

Additional things:

• the Operation error field is never used
• on a cache miss, a PRECONDITION_FAILURE status should be returned, with appropriate MISSING type Violations for each digest, and the digests.
• if any errors can occur before actual execution, they should be a gRPC status

from bazel-buildfarm.

when the execution times out, a DEADLINE_EXCEEDED status should be returned in the ExecuteResponse status field. It should never be returned as the gRPC status, because that means a different thing semantically.

This is already happening - on timeout, executeCommand will return DEADLINE_EXCEEDED which will be used to set the ExecuteResponse status field.

from bazel-buildfarm.

This was accomplished recently with #218, closing

from bazel-buildfarm.