Now any set of widgets and rows can be placed in a we-collapse element
so that those elements can be foldable. The first element inside (or
the mentioned "string" on the we-collapse element itself) is used as the
always shown element (with a toggler on its left to toggle the
visibility of the other items).
we-collapse inside other we-collapse is supported as well.
Limitations / Other infos:
- The use of '⌙' and   characters is not automatic (yet?).
Sometimes it actually make sense to use them without a we-collapse or
to not use them in a we-collapse.
- The use of we-collapse is limited to widgets inside the same option.
So unfortunately, there is no current way to add all bg image options
in a folable section as those contain many different options. Maybe
in the future.
Part of https://github.com/odoo/odoo/pull/56350closesodoo/odoo#56352
X-original-commit: d9c450ac97de40c71aebd487cff725bfda6a577b
Signed-off-by: Quentin Smetz (qsm) <qsm@odoo.com>