Updates the various gRPC/protobuf libs (google.golang.org/grpc/... and github.com/golang/protobuf/proto) and the boulder-tools image so that we can update to the newest github.com/grpc-ecosystem/go-grpc-prometheus. Also regenerates all of the protobuf definition files.
Tests run on updated packages all pass.
Unblocks #2633fixes#2636.
This is a roll-forward of 5b865f1, with the QueueDeclare and QueueBind changes
in AMQP-RPC removed, and the startup order changes in test/startservers.py
removed. The AMQP-RPC changes caused RabbitMQ permission problems in production,
and the startup order changes depended on the AMQP-RPC changes but were not
required now that we have a unittest also.
This allows us to restart backends with relatively little interruption in
service, provided the backends come up promptly.
Fixes#2389 and #2408