[FIX] l10n_eu_services:apply tag from localization

This commit aims to allow assigning tags to the taxes
created by the OSS feature by providing the xml_id of their
report.line in the eu_tag_map.py file.

Before this commit:
In l10n_be, the taxes created by OSS (l10n_eu_services) didn't set
the tag +47 on invoice_repartition_lines nor +49 on
refund_repartition_lines.
This make the VAT report for Belgium wrong.

After this commit:
Taxes created by OSS for a company using the belgian CoA will get
their tags set properly and thus will the taxes impact the
belgian tax report correctly.

task: 2770182
ticket: 2768622

Community-PR: https://github.com/odoo/odoo/pull/85607



Design choices:
This fix is currently solving the issue for l10n_be but we have
no doubt that it will be raised for other EU countries too.

In order to provide the tags, we decided to be consistent with
what as been done regarding the tax mapping. Thus we decided to
create and maintain a simple mapping file and to test it.

several other methods were explored:
- create a global variable and update it from all localization
modules. This method would work but is ugly and error prone.

- create a templating method and override it from localization
modules.
The problem is where to set the root of the template method?
The naïve solution would be to create a bridge module between
l10n_eu_services and l10n_be but that would lead to an explosion
in the number of bridge modules which we don't want.

In order to keep things simple and generic, we could put the
template method directly into the account module. But it is kind
of ugly because account shouldn't know anything about the oss
feature and it would encourage such a leaky design to happen
again in the future.

closes odoo/odoo#85607

Signed-off-by: William André (wan) <wan@odoo.com>