Before this commit an ir_assets generated automaticaly by the web editor
will generate an url ending with ...custom.addon.bundle_name.ext
After this commit the url will start with /_custom/addon.bundle_name/...
This will make it easier to spot at immediately if it is a custom asset
and thus it is useless to apply the glob. Actually, it will fail on the
/_custom when trying to glob, making it faster.
This is mainly useful to clarify and debug but in a case with mainly
customised ir_asset for one bundle, it may have an impact on speed.
An upgrade script was created for this change.
closesodoo/odoo#120699
Related: odoo/upgrade#4636
Signed-off-by: Xavier Dollé (xdo) <xdo@odoo.com>