Numeric parsing functions that support number separators and suffixes

Following #10480, there's currently no parsing function that deals with separators and suffixes. While we don't necessarily need this in `Std.parseInt` and `Std.parseFloat`, it would be good to have _some_ function that knows how to deal with this.

Start by reading issue #10480 and the existing Std.parseInt and Std.parseFloat APIs to understand current parsing behavior and the intended scope. The issue does not define the new function's API or separator and suffix rules, so done requires an agreed design and documented behavior for parsing those forms.

Written by the indexing model from the issue text.