feat: clear get_mfes cache before adding custom mfes
Description
The tutor-MFE plugin recently started caching the MFE_APPS hook.
This resulted in the custom MFEs that we add/update through this plugin not getting applied because we modify the MFE_APPS hook only after the project root is ready, but the caching occurs before this event.
To resolve this, we are now clearing the cache when modfying the MFE_APPS hook, so that these modifications gets added to the cache.
Additional context
Edited by Kaustav Banerjee