cmdutil: narrow scope of KeyError in makefilename() It seemed too broad to catch a standard Python exception.

node: make bin() be a wrapper instead of just an alias This includes a full backout of 59affe7e and 30d0cb27. Per the review of the former, we'd rather adapt the API to behave like it used to (at least for now), and take a second run at it if it shows up in our performance numbers. I ran perfrevlogindex with and without this change and it didn't make a measurable difference, so maybe it's fine (despite my intuition to the contrary). Differential Revision: https://phab.mercurial-scm.org/D2279