[checkoutlinesufo] suggestion: remove `-e` option (or be even more radical)

[frankrolf]

checkoutlinesufo used to be a tool to (literally) “check” outlines.
Traces of this are found in previous issues, such as #208 or #209.

Today, checkoutlinesufo is almost exclusively used to remove overlaps before building CFF fonts.
This makes the option -e a bit anachronistic, and difficult to explain (see also my ongoing confusion about the -e option in #1090).

I assume that -e originally was supposed to be a “failsafe” mode, since the original checkoutlines could be run on OTF/PFA files. Today, this is not really necessary, since checkoutlinesufo does by default write into the glyphs.com.adobe.type.processedglyphs layer.

I suggest one of two ways forward:

1‍⃣ remove the -e option from checkoutlinesufo altogether

2‍⃣

• leave checkoutlinesufo alone but emit a deprecation warning
• create a new tool with a new name (removeoverlapufo ?), which mirrors the functionality of checkoutlinesufo, but has more straightforward argument logic (and no -e option)