fix: exclude provisioner_state from workspace_build_with_user view (#22159)

The provisioner state for a workspace build was being loaded for every
long-lived agent rpc connection. Since this state can be anywhere from
kilobytes to megabytes this can gradually cause the `coderd` memory
footprint to grow over time. It's also a lot of unnecessary allocations
for every query that fetches a workspace build since only a few callers
ever actually reference the provisioner state.

This PR removes it from the returned workspace build and adds a query to
fetch the provisioner state explicitly.

coderd/database/dump.sql

@@ -2708,7 +2708,6 @@ CREATE VIEW workspace_build_with_user AS
     workspace_builds.build_number,
     workspace_builds.transition,
     workspace_builds.initiator_id,
-    workspace_builds.provisioner_state,
     workspace_builds.job_id,
     workspace_builds.deadline,
     workspace_builds.reason,