[FW][FIX] hr_holidays: fix accrual plan in hours

[fw-bot]

Steps

• create an accrual plan with a level giving 1 hour every month and a carry
  over with a maximum of 4 hours. Set accrued gain time at the start of the period
  and carry-over time at start of the year.
• create an allocation using this accrual plan, for a time off type in days,
  set the start date on the first day of next year.
• go to Time Off Dashboard
• check the balance on the middle of the month of the following year (e.g.
  15 january 2026 if the allocation starts on 1 january 2025).

-> ~14 days of time off available: the max postpone amount is not applied,
the time gained is in days and not in hours and more than 1 day is gained/month
(balance a few days after the start of the allocation should be +1 added_value
but is more than that).

Causes:

• the maximum amount of carry over postpone_max_days is applied in days
  even if the accrual added_value is in hours and the UI shows postpone_max_days
  as "Up to X hours".
• get_future_leaves returns a number of hours if the allocation is in hours, even
  if the time off type is in days.
• the number of hours from the accrual at the beginning of the allocation is too
  high if the start of the accrual is in the future and gain time added at the start
  of the period due to cache not being invalidated.
  

  odoo/addons/hr_holidays/models/hr_leave_allocation.py

  Lines 575 to 578 in 19c7737

  	if self.type_request_unit in ['hour']:
  	return float_round(fake_allocation.number_of_hours_display - self.number_of_hours_display, precision_digits=2)
  	res = round((fake_allocation.number_of_days - self.number_of_days), 2)
  	fake_allocation._invalidate_cache(['number_of_days', 'number_of_days_display', 'lastcall', 'nextcall', 'number_of_hours_display'])

opw-4272315

Forward-Port-Of: #195361
Forward-Port-Of: #185699

[robodoo]

[fw-bot]

@taqu-odoo @Bertrand2 this PR targets master and is the last of the forward-port chain.

To merge the full chain, use

@robodoo r+

More info at https://github.com/odoo/odoo/wiki/Mergebot#forward-port

[taqu-odoo]

robodoo r+