add system signatures to FunctionSignatures

[holic]

we have a use case in dev tools for decoding callFrom with a world function selector where we want to ultimately display the system function signature in our "action logs"

it would help to be able to look up these signatures onchain as needed

(related to #2386)

[yonadaaa]

fyi in Sky Strife there is a transaction explorer that displays the function names of call, callFrom and batchCall calls. It uses the world contracts onWrite hook though so it doesn't have to work back from a selector

edit: actually for batch calls it uses the ABI to decode the call

[holic]

decided we'll just do "add system signatures" part for now and avoid the cost of onchain table until we have a good use case for it

[holic]

while we do this, we should also rename functionSelector key to worldFunctionSelector in FunctionSelectors table

so that it's clear that FunctionSelectors table are for world function selectors (and can be used as source of truth for generating world ABI)

while FunctionSignatures is just a generic registry for offchain stuff (translating ~any function selector to signature and back)

[holic]

added in #2392 and #2395