[FIX] web: client-side RPC error to have an arguments data member

Several XHR error handlers expect a data.arguments member which holds
the args tuple from the Python exception.

Some have alternate codepaths for "xhr errors" but several
don't (e.g. addons/payment/static/src/js/payment_form.js:142,
addons/web/static/src/js/services/crash_manager.js:229,
addons/website/static/src/js/content/website_root.js:167) and will
thus blow up on synthetic client-side xhr errors.

Modify the synthetic errors so they provide that member as an array.