VAULT-33758: IPv6 address conformance for proxy and agent (#29517)

This is a follow-up to our initial work[0] to address RFC-5952 §4 conformance for IPv6 addresses in Vault. The initial pass focused on the vault server configuration and start-up routines. This follow-up focuses on Agent and Proxy, with a few minor improvements for server.

The approach generally mirrors the server implementation but also adds support for normalization with CLI configuration overrides.

One aspect we do not normalize currently is Agent/Proxy client creation to the Vault server with credentials taken from environment variables, as it would require larger changes to the `api` module. In practice this ought to be fine for the majority of cases.

[0]: https://github.com/hashicorp/vault/pull/29228

command/debug.go

@@ -25,6 +25,7 @@ import (
 	"github.com/hashicorp/go-secure-stdlib/strutil"
 	"github.com/hashicorp/vault/api"
 	"github.com/hashicorp/vault/helper/osutil"
+	"github.com/hashicorp/vault/internalshared/configutil"
 	"github.com/hashicorp/vault/sdk/helper/jsonutil"
 	"github.com/hashicorp/vault/sdk/helper/logging"
 	"github.com/hashicorp/vault/version"
@@ -211,7 +212,7 @@ Usage: vault debug [options]
   output. The command uses the Vault address and token as specified via
   the login command, environment variables, or CLI flags.
 
-  To create a debug package using default duration and interval values in the 
+  To create a debug package using default duration and interval values in the
   current directory that captures all applicable targets:
 
   $ vault debug
@@ -495,7 +496,7 @@ func (c *DebugCommand) preflight(rawArgs []string) (string, error) {
 
 	// Populate initial index fields
 	c.debugIndex = &debugIndex{
-		VaultAddress:           client.Address(),
+		VaultAddress:           configutil.NormalizeAddr(client.Address()),
 		ClientVersion:          version.GetVersion().VersionNumber(),
 		ServerVersion:          serverHealth.Version,
 		Compress:               c.flagCompress,