[I18N] *: create a saas-15.3 specific project

Until know, Transifex projects were organised as:
- odoo-14
- odoo-15
- odoo-master

with odoo-master changing frenquently to reflect the
last used saas version, to prepare the future odoo-16 version.

This was ok as most people used stable versions at that time.

Now the saas versions are frequently released and many users of
odoo.com are running these versions, the quality of translations is
more important and preparing for the future version is not the only
goal.

Having only one project synchronised with a saas version is not enough
as we frenquently have to support multiple versions in parallel
(e.g. saas-15.2 for users and saas-15.3 for odoo.com).

Switch to a project for each saas release to be more flexible.
Hopefully, it won't be too much additional work for translators thanks
to TM.

New organisation
- odoo-14
- odoo-15
- odoo-s15-2
- odoo-s15-3

and delete projects when it is no longer supported

closes odoo#94010

X-original-commit: bb071a9
Related: odoo/enterprise#28588
Signed-off-by: Martin Trigaux (mat) <[email protected]>

Author: mart-e