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/resolver/resolver.go

@@ -182,6 +182,7 @@ type BuildOptions struct {
 
 // An Endpoint is one network endpoint, or server, which may have multiple
 // addresses with which it can be accessed.
+// TODO(i/8773) : make resolver.Endpoint and resolver.Address immutable
 type Endpoint struct {
 	// Addresses contains a list of addresses used to access this endpoint.
 	Addresses []Address
@@ -332,6 +333,11 @@ type AuthorityOverrider interface {
 	// OverrideAuthority returns the authority to use for a ClientConn with the
 	// given target. The implementation must generate it without blocking,
 	// typically in line, and must keep it unchanged.
+	//
+	// The returned string must be a valid ":authority" header value, i.e. be
+	// encoded according to
+	// [RFC3986](https://datatracker.ietf.org/doc/html/rfc3986#section-3.2) as
+	// necessary.
 	OverrideAuthority(Target) string
 }