Registry tool ease-of-use and server performance improvements

This includes minor improvements to the registry tool command-line experience:

Bulk (parallel) actions generally only warn when individual actions fail. Previously some would exit.
Usage information is not printed when registry get doesn't find anything (usage information is usually irrelevant and distracting in these situations).

The registry-server also has performance and monitoring improvements, notably:

Indexes were added to speed listing of artifacts under revisioned resources (specs and deployments).
Support for Prometheus monitoring was added.

Changelog

b9f77d1 WorkerPools always warn (and never exit on errors) (#1077)
c46b9de When registry get matches nothing, print "Not Found" to stderr and don't report an error. (#1073)
4ee8fd6 instrument for prometheus (#1076)
50ec9b4 Add indexes to specs and deployments. (#1071)
d9a0ebf Unhide generated rpc commands for Admin and Provisioning methods. (#1074)
a405b01 Add benchmark that lists artifacts under each resource type. (#1068)
3248ec6 read nightly build for docker (#1067)
a3511c9 Fix error in README (#1063)
db1f198 Update golangci-lint version (#1064)
8b55e1e update github workflows and actions (#1065)
d412d6c Replace wildcards with specific file names in download script. (#1062)