Don't write new file when inserting embed line

Instead, load the relevant module of the true file, and execute the modified code within that.

This also cleans up some of the previous now-unnecessary code around get_module_with_inserted_embed_line

manimlib/module_loader.py

@@ -76,10 +76,7 @@ class ModuleLoader:
         builtins.__import__ = tracked_import
 
         try:
-            # Remove the "_insert_embed" suffix from the module name
             module_name = module.__name__
-            if module.__name__.endswith("_insert_embed"):
-                module_name = module_name[:-13]
             log.debug('Reloading module "%s"', module_name)
 
             spec.loader.exec_module(module)