ipn/ipnlocal: sort profiles by date created when possible (#20223)

This adds a Created field to LoginProfile to normalize the sort order
of login profiles presented in the various client GUIs. The default
sort order for existing profiles remains unchanged and continues to be
based on Name. Newly added profiles will be stamped at creation time
and returned at the top of the list of unstamped profiles, sorted by
creation date in descending order.

The rationale is to ensure that all clients present the user's profile
list in the same order, regardless of newly added accounts, name
changes, or nickname overrides.

The Mac client was recently updated to remove various custom profile
sorting behaviors (https://github.com/tailscale/corp/pull/43847).
iOS, Android, and Windows do not currently perform GUI-level sorting,
so this change should propagate to them seamlessly.

updates tailscale/corp#43843

Signed-off-by: Will Hannah <willh@tailscale.com>

ipn/ipn_clone.go

@@ -8,6 +8,7 @@ package ipn
 import (
 	"maps"
 	"net/netip"
+	"time"
 
 	"tailscale.com/drive"
 	"tailscale.com/tailcfg"
@@ -38,6 +39,7 @@ var _LoginProfileCloneNeedsRegeneration = LoginProfile(struct {
 	NodeID         tailcfg.StableNodeID
 	LocalUserID    WindowsUserID
 	ControlURL     string
+	Created        time.Time
 }{})
 
 // Clone makes a deep copy of Prefs.