Following new policies in terms of product design-language, this commit
will partially revert 546477d reducing the number of `oi` icons.
It will also improve rendering when icons are rendered at our default
font-size (13px), avoiding blur effects when icons use thin lines.
Since fontAwesome will coexists with `oi` longer than expected, the
commit will also review size utility-classes in order to get consistent
result when used in conjunction with fa's ones (notably `fa-lg`).
Part-of: odoo/odoo#85651
stefanorigano (SRI)
28f910f5be