[FIX] hr_holidays: fix traceback to add timezone

Currently, Traceback occurs when we do timezone filters in every one
report of time off because the timezone is non-stored compute field in
hr leave model.

So in this commit, get the timzone value based on compute field from
resource or timezone of the current company's calendar OR user's tz
and at last 'UTC'.

closes odoo/odoo#57597

Taskid: 2334866
Signed-off-by: Yannick Tivisse (yti) <yti@odoo.com>