core: Variadic Context.Logger(); soft deprecation

Ideally I'd just remove the parameter to caddy.Context.Logger(), but
this would break most Caddy plugins.

Instead, I'm making it variadic and marking it as partially deprecated.
In the future, I might completely remove the parameter once most
plugins have updated.

modules/caddyhttp/push/handler.go

@@ -61,7 +61,7 @@ func (Handler) CaddyModule() caddy.ModuleInfo {
 
 // Provision sets up h.
 func (h *Handler) Provision(ctx caddy.Context) error {
-	h.logger = ctx.Logger(h)
+	h.logger = ctx.Logger()
 	if h.Headers != nil {
 		err := h.Headers.Provision(ctx)
 		if err != nil {