Auto merge of #122013 - Swatinem:unicode-gen-fastpath, r=scottmcm

Add a lower bound check to `unicode-table-generator` output

This adds a dedicated check for the lower bound
(if it is outside of ASCII range) to the output of the `unicode-table-generator` tool.

This generalized the ASCII-only fast-path, but only for the `Grapheme_Extend` property for now, as that is the only one with a lower bound outside of ASCII.

Author: bors