Add method to config to determine if job is public [#78774326]
Add method on Build to determine if it's a one-off [#78774326]
API respects publically viewable flag for build event stream [#78774326]

Also, make contracts about DBs between main, api handler, and individual servers
simpler, and more consistent.
Eliminate some fakes
Slight refactor of default config db test
Refactor db shared example to require less global setup, and enable focus/pend
Stop dot-importing package under test for all db spec
Privatize api server structs