[REF] [crm_]mail_client_extension, base_setup, crm[_iap_lead_enrich], iap:...

[REF] [crm_]mail_client_extension, base_setup, crm[_iap_lead_enrich], iap: split mail specific and crm specific code

- split the mail_client_extension module onto two modules:
  1) module mail_client_extension having mail/contact specific code,
  depends on iap and contacts only
  2) module crm_mail_client_extension having crm specific code,
  depends on CRM and mail_client_extension.

  Purpose is to allow the user to use the mail_client_extension
  without needing to install CRM, this will also allow
  the usage of the mail connector in other modules without
  the need for CRM.

- add the module_mail_client_extension field to the
  res_config_settings model of the base_setup module
  in order to enable the user to install the
  mail_client_extension module directly from the settings

- move the crm_lead model from the mail_client_extension_module
  to the newly created crm_mail_client_extension_module, as this
  model is no longer needed by the mail_client_extension module
  because it no longer not implemants CRM functionality

- move the iap_enrich_api model from the crm_iap_lead_enrich
  module onto the iap module as it is only related to contacts
  and not to CRM, this way it can be used in other modules such
  as the mail_client_extension module without the need for CRM
  module

Task-2382870
UPG-PR: https://github.com/odoo/upgrade/pull/2156
COM-PR: https://github.com/odoo/odoo/pull/66139