Stop the slow test packages waiting (closes #263)

The slowest test packages spent their time waiting rather than testing.

db.Params gains an optional PasswordCost (zero means bcrypt.DefaultCost), and the db, ircserver and handlers tests hash at bcrypt.MinCost. A test IRC server's relay checks its queue on broker notification instead of polling. The service and handlers tests build config.Config directly and run in parallel; config exports DefaultTrustedProxies and ParseTrustedProxies for them. Fixed sleeps give way to waits for the event. Production defaults are unchanged.

What still takes time is CPU work under -race or a timeout a test is about.

Model: opus-5-5

internal/ircserver/integration_test.go

@@ -3,7 +3,6 @@ package ircserver_test
 import (
 	"strings"
 	"testing"
-	"time"
 
 	"sneak.berlin/go/neoirc/internal/config"
 )
@@ -1508,9 +1507,6 @@ func TestIntegrationThirdClientObserver(t *testing.T) {
 	bob.joinAndDrain("#trio")
 	carol.joinAndDrain("#trio")
 
-	// Drain join notifications.
-	time.Sleep(100 * time.Millisecond)
-
 	// alice sends; both bob and carol should receive.
 	alice.send("PRIVMSG #trio :hello trio")