chore: fix flakiness in gofakeit usage with additional random string (#10385)

# Which Problems Are Solved

Flakiness in integration tests regarding gofakeit functions, which
provided the same names on 2 different occasions.

# How the Problems Are Solved

Attach a random string to the provided names, so that they are not
dependent on the gofakeit code.

# Additional Changes

None

# Additional Context

None

---------

Co-authored-by: Marco A. <marco@zitadel.com>

internal/integration/rand.go

@@ -6,7 +6,7 @@ import (
 )
 
 func init() {
-	rand.Seed(time.Now().UnixNano())
+	rand.NewSource(time.Now().UnixNano())
 }
 
 var letterRunes = []rune("abcdefghijklmnopqrstuvwxyz")