Make AWM Primary Network Optimization configurable

[martineckardt]

Context and scope
When running a Subnet with all validators in partial sync mode, it will not be able to verify incoming messages from the primary network. The optimization will try to gather signatures over the C-Chain's message from the Subnet's validator set. Since these do not sync the C-Chain they won't be able to sign the message.

We should make this optimization configurable.

Discussion and alternatives
TBD

Open questions
TBD

[michaelkaplan13]

FWIW, this optimization will need to be removed all together in the E upgrade in order to allow for subnets with only subnet-only validators to verify messages from the C-Chain. This will also need to be accounted for in the awm-relayer so that it is able to determine which validators to query for BLS signatures.

[aaronbuchwald]

It could still be configurable in the E Upgrade if subnets opt in to validating the C-Chain. I'm not opposed to removing it completely in the E Upgrade if that's the easiest path, but it's worth evaluating the performance of aggregating a signature from >= 67% of the primary network before making that decision.