Capture more call meta-info

[ggreif]

Along with the caller of the message we could also make available to the method body

• availableCycles the cycles sent along with the message
• rawArguments the undecoded Candid message
• deadline for best-effort calls ("response due")
• maybe others?

It would also be interesting to specify a minimumCycles = 10_000 there, which would immediately check (before Candid decoding) if the message has enough cycles for the method to perform its work. This would be useful for pay-for-work canisters.