Use mcdsl/terminal for all password prompts

Replace direct golang.org/x/term calls with mcdsl/terminal.ReadPassword
across mciasctl (6 sites), mciasgrpcctl (1 site), and mciasdb (1 site).
Aligns with the new CLI security standard in engineering-standards.md.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

vendor/google.golang.org/grpc/balancer/balancer.go

@@ -75,8 +75,6 @@ func unregisterForTesting(name string) {
 
 func init() {
 	internal.BalancerUnregister = unregisterForTesting
-	internal.ConnectedAddress = connectedAddress
-	internal.SetConnectedAddress = setConnectedAddress
 }
 
 // Get returns the resolver builder registered with the given name.