Separate caching of dynamic user vars from permissions

[licitdev]

Closes #9933.

The permissions are now cached based on role in systemCache.

The dynamic user variables are cached in cache per user when CACHE_ENABLED is true.

The cache is cleared upon create, update, and delete actions on items when CACHE_AUTO_PURGE is true.

On a side note, the caching may not be efficient if users are using the app when CACHE_AUTO_PURGE is true. The cache is cleared on every page navigation due to an update being performed in /users/me/track/page. However, that is the intended behaviour in case someone requires to use $CURRENT_USER.last_page in permissions.

Functions extracted

1. parsePermissions() to parse and extract required dynamic fields
2. getFilterContext() to fetch dynamic fields only when necessary
3. processPermissions() to process the filters with the filterContext

[azrikahar]

LGTM!