[REF] website, *: improve use of unicode support font

* web, theme_bootswatch

Improvement of https://github.com/odoo/odoo/commit/02a321cffb2da60a86b960e75c445e37094567b4

- Clarify the name of the support font (to distinguish it from standard
  and google fonts and avoid confusion with Noto Sans and Noto Serif).

- Make sure the support font is added and can be added for all font
  definitions in odoo scss files thanks to a scss function.

Could be backported in 12.0 if judged necessary.

Part of https://github.com/odoo/odoo/pull/37293