[IMP] crm_iap_lead_enrich: improve settings of enrichment

Before this commit it was not possible to enrich leads manually as
only a cron enriches leads. It is considered as sub optimal since people
would like to do it manually on some leads and not activate it only for
all leads, using a cron.

After this commit an option is added in CRM settings to choose the type of
enrichment: either manual, either automatic.

In manual mode, a button appears on the lead to enrich if certain conditions
are met (email_adress present, not already enriched,...). It also deactivates
the enrich cron.

In automatic mode, the button on lead is not displayed and the cron is
activated.

A config parameter is defined in CRM as it is requested to be able to configure
it directly in CRM without having to first install the app then configure
it. A post install hook to synchronize cron status with config parameter
is therefore required.

FP/AJU request

Task 2075817

closes odoo/odoo#37367

Signed-off-by: Thibault Delavallee (tde) <tde@openerp.com>