Support merge_fields and language parameters for the Mail Subscribe rules action

Problem/Motivation

We have clever_reach_rules_mail_subscribe rules action that supports only List ID and Mail parameters.
Need to have support apply the Merge Fields and Language parameters, like in the clever_reach_rules_user_subscribe rules action.

Proposed resolution

Update the clever_reach_rules_mail_subscribe rules action, add merge_fields and language parameters like in the clever_reach_rules_user_subscribe rules action.