global-endpoint: Refactor to auto-allocate badges

As the global-endpoint is a notification object shared across multiple
camkes connections, we force each connection end to have a distinct
badge value and don't allow the camkes assembly to specify badge values
or notification object names.

global-endpoint: Provide method to get badge value

Components can call this method to get the badge value of notifications
belonging to the connection this object is used in.

rpc-get-notification: Rename rpc-get-notification to get-notification

This template file will be included by different files which are not
necessarily related to RPC connectors.