Stop the slow test packages waiting (closes #263)

- Tests hash passwords at bcrypt.MinCost through db.PasswordCost.
- Test IRC servers check the queue only on broker notification;
  one test keeps the 100 ms fallback poll.
- The stop-timeout test shortens the timeout through a test-only
  setter.
- service and handlers tests build config.Config directly instead
  of through config.New, so they run in parallel: service had run
  serially, and handlers started its servers one at a time.
- Repeated race trials run as parallel subtests.
- Fixed sleeps become waits on the broker.
- A new test covers the relay's failed queue read, which only the
  100 ms poll had reached.

Model: opus-5-5

internal/db/db_test.go

@@ -10,6 +10,7 @@ import (
 	"time"
 
 	"go.uber.org/fx/fxtest"
+	"golang.org/x/crypto/bcrypt"
 	"sneak.berlin/go/neoirc/internal/config"
 	"sneak.berlin/go/neoirc/internal/db"
 	"sneak.berlin/go/neoirc/internal/dbtest"
@@ -29,6 +30,13 @@ const (
 	endlessQueryTimeout = 100 * time.Millisecond
 )
 
+func TestMain(m *testing.M) {
+	// A password hashed at full cost takes seconds under -race.
+	db.PasswordCost = bcrypt.MinCost
+
+	m.Run()
+}
+
 // TestDefaultDBURLSetsWALAndBusyTimeout opens a file database
 // with the default URL's parameters the way the server does,
 // and checks the journal mode and busy timeout it ends up with.