✨ Rewrite STARTSWITH and ENDSWITH as operators

[joocer]

Like we rewrite a LIKE '%s%' to a InStr 's' rewrite so that starts and ends are special internal operators (ones that users can't use)

StartsWith IStartsWith NotStartsWith INotStartsWith EndsWith IEndsWith NotEndsWith INotEndsWith

This could take advantage of not building arrays of constants, not casting to numpy, which is approximately 12 seconds on 100m rows.