modules: remove include of private.h

Remove some includes of private.h
Add some methods to get the mempool of client and context so that we can
remove direct access.
Move some things around.
Use methods to get pw_loop variables.

See #3243

src/modules/module-protocol-native/v0/typemap.h

@@ -1,3 +1,13 @@
+enum spa_node0_event {
+	SPA_NODE0_EVENT_START   = SPA_TYPE_VENDOR_PipeWire,
+	SPA_NODE0_EVENT_RequestClockUpdate,
+};
+
+enum spa_node0_command {
+	SPA_NODE0_COMMAND_START = SPA_TYPE_VENDOR_PipeWire,
+	SPA_NODE0_COMMAND_ClockUpdate,
+};
+
 static const struct type_info {
 	const char *type;
 	const char *name;