feat(tsconnect): add getCert, listenTLS, setFunnel + fix TLS cert for WASM

Enable ACME TLS certificates on js/wasm by dropping the !js build tag from
cert.go and routing storage through the state store. Add getCert, listenTLS,
and setFunnel WASM bindings with a combinedTLSListener that merges Funnel
ingress and direct tailnet connections. Notify the control plane immediately
after serve config changes to accelerate Funnel DNS provisioning.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

ipn/ipnlocal/local.go

@@ -412,6 +412,10 @@ type LocalBackend struct {
 	// See [LocalBackend.ConfigureCertsForTest].
 	getCertForTest func(hostname string) (*TLSCertKeyPair, error)
 
+	// acmeHTTPClient, if non-nil, is used for all ACME HTTP requests instead
+	// of http.DefaultClient. Set via SetACMEHTTPClient before first cert use.
+	acmeHTTPClient *http.Client
+
 	// existsPendingAuthReconfig tracks if a goroutine is waiting to
 	// acquire [LocalBackend]'s mutex inside of [LocalBackend.AuthReconfig].
 	// It is used to prevent goroutines from piling up to do the same