[FIX] hr_payroll: Make payroll groups imply holiday groups

Purpose
=======

Currently, groups `hr_holidays.group_hr_holidays_[user|manager]`
and `hr_payroll.group_hr_payroll_[user|manager]` are independant.

A member of payroll groups is not able to approve/refuse a leave.

This is a problem as they should be able to approve/refuse leaves before generating payslips.
This is the  point of `hr.benefits`: a global way of managing
attendances and leaves before generating payslips.

Specification
=============

Payroll groups should imply the corresponding
holiday group.

1. User
`hr_payroll.group_hr_payroll_user`
implies
`hr_holidays.group_hr_holidays_user`

2. Manager
`hr_payroll.group_hr_payroll_manager`
implies
`hr_holidays.group_hr_holidays_manager`

addons/hr_payroll/security/hr_payroll_security.xml

@@ -10,13 +10,13 @@
     <record id="group_hr_payroll_user" model="res.groups">
         <field name="name">Officer</field>
         <field name="category_id" ref="base.module_category_human_resources_payroll"/>
-        <field name="implied_ids" eval="[(4, ref('hr.group_hr_user')), (4, ref('hr_contract.group_hr_contract_manager'))]"/>
+        <field name="implied_ids" eval="[(4, ref('hr.group_hr_user')), (4, ref('hr_contract.group_hr_contract_manager')), (4, ref('hr_holidays.group_hr_holidays_user'))]"/>
     </record>
 
     <record id="group_hr_payroll_manager" model="res.groups">
         <field name="name">Administrator</field>
         <field name="category_id" ref="base.module_category_human_resources_payroll"/>
-        <field name="implied_ids" eval="[(4, ref('hr_payroll.group_hr_payroll_user'))]"/>
+        <field name="implied_ids" eval="[(4, ref('hr_payroll.group_hr_payroll_user')), (4, ref('hr_holidays.group_hr_holidays_manager'))]"/>
         <field name="users" eval="[(4, ref('base.user_root')), (4, ref('base.user_admin'))]"/>
     </record>