This commit reworks a little bit the backend assets to remove a
bundle and thus save a call at webclient startup. The bundle
"assets_backend_prod_only" existed only to allow to add files in
production, but not in the tests (typically, the file that spawns
the webclient).
This commit introduces a new bundle "web.assets_web" that contains
"assets_backend" and the few files that we only want in production.
In the /web page, we now load "assets_web" instead of
"assets_backend" and "assets_backend_prod_only". In the /web/tests
page, we keep loading "assets_backend", which is now directly
included into "web.tests_assets".
For the sake of consistency, this commit also renames the dark
mode bundle "dark_mode_assets_backend" into "assets_web_dark".
closesodoo/odoo#135204
Related: odoo/enterprise#47316
Signed-off-by: Samuel Degueldre (sad) <sad@odoo.com>