EPIC: FVM Syscall Precompiles

[Stebalien]

We need precompiles for various syscalls:

• actor::resolve_address
• actor::lookup_address
• actor::get_actor_code_cid
• rand - we should have a single "rand" precompile that can return both chain and beacon randomness.
• vm::context (actor IDs, etc). punting because we can get almost all of this information from other sources.

We don't need precompiles for:

• crypto::verify_signature - the Ethereum precompile is general-purpose enough to cover this.
• crypto::hash
  • sha256 and blake2b are already supported.
  • we can revisit this later.
• state related things
• miner-specific crypto functions

[maciejwitowski]

@mriise is it something you'll be able to handle as precompiles expert?