What is the extra slot used for? (I.e. why not just `MAX_SIGNALS` elements?)
What is the extra slot used for? (I.e. why not just `MAX_SIGNALS` elements?)

_Originally posted by @neobrain in https://github.com/FEX-Emu/FEX/pull/1613#discussion_r823493879_

This is an antipattern seen through our signal handling due to signals using 1 based indexing with 0 being special cased.
Resolve this pattern and come back to it.