In 746f667 I "optimized" wal_acceptor tests by setting "--pageserver"
flag only on one of wal_acceptors. Which obviously will hang the system if
that wal_acceptors is down. And test_acceptors_restarts does exctly this.
Set "--pageserver" on all wal_acceptors as it was before.
This patch started as an effort to support CLI working against remote
pageserver, but turned into a pretty big refactoring.
* CLI now does not look into repository files directly. New commands
'branch_create' and 'identify_system' were introduced into page_service to
support that.
* Branch management that was scattered between local_env and
zenith/main.rs is moved into pageserver/branches.rs. That code could better fit
in Repository/Timeline impl, but I'll leave that for a different patch.
* All tests-related code from local_env went into integration_tests/src/lib.rs as an
extension to PostgresNode trait.
* Paths-generating functions were concentrated around corresponding config
types (LocalEnv and PageserverConf).
