Currently, spreadsheet dashboards always display numbers with the en_US
format, no matter the user's lang.
That's because the locale is hardcoded in the spreadsheet source file, in
the source code (or it falls back to the default en_US locale if it's missing).
With this commit, we dynamically change the spreadsheet locale with the user's
locale when he loads a dashboard.
We can change the locale with every user because the dashboard is readonly.
It cannot create a giant mess with dates in various locales.
Limitation
----------
Since hardcoded date formats are not changed when the locale changes, dates
will keep the en_US format. However, most (if not all) dates in dashboards
are coming from ODOO.PIVOT and ODOO.LIST functions, which compute the formats
dynamically based on the current locale.
closesodoo/odoo#135119
Task: 3484002
Related: odoo/enterprise#47284
Signed-off-by: Rémi Rahir (rar) <rar@odoo.com>