[FW][FIX] formula assistant: localize argument separator

[fw-bot]

Description

The argument separator in the formula assistant was not localized, it was always a comma no matter the locale. This commit fixes it.

Task: : 3789860

review checklist

• feature is organized in plugin, or UI components
• support of duplicate sheet (deep copy)
• in model/core: ranges are Range object, and can be adapted (adaptRanges)
• in model/UI: ranges are strings (to show the user)
• undo-able commands (uses this.history.update)
• multiuser-able commands (has inverse commands and transformations where needed)
• new/updated/removed commands are documented
• exportable in excel
• translations (_t("qmsdf %s", abc))
• unit tested
• clean commented code
• track breaking changes
• doc is rebuild (npm run doc)
• status is correct in Odoo

Forward-Port-Of: #3871
Forward-Port-Of: #3790

[robodoo]

Pull request status dashboard.

[fw-bot]

This PR targets saas-17.2 and is part of the forward-port chain. Further PRs will be created up to master.

More info at https://github.com/odoo/odoo/wiki/Mergebot#forward-port

[fw-bot]

@hokolomopo @LucasLefevre ci/runbot failed on this forward-port PR

[hokolomopo]

@robodoo r+

[fw-bot]

@hokolomopo @LucasLefevre this PR was modified / updated and has become a normal PR. It should be merged the normal way (via @robodoo)

[fw-bot]

Forward-porting to 'saas-17.2' (from #3882).