Proto commits in backtrace-labs/umash

These 2 commits are when the Protocol Buffers files have changed:

Commit:4fdb66b
Author:Paul Khuong

exact_test_sampler: add a "status" method And use that to check for connection health in exact_test_sampler_client. TESTED=manually.

The documentation is generated from this commit.

Commit:e2d70a6
Author:Paul Khuong
Committer:Paul Khuong

t/exact_test_sampler: parallel eval through a gRPC stub lookalike We can run the Monte Carlo simulations on any machine; let's write a gRPC server to handle evaluation requests, and more easily burn CPU cycles all around the planet. For now, make exact_test_sampler call into a dummy ExactTestSampler implementation, where only the input values are protos. TESTED=existing tests; bench.sh still runs.