Execute proposal on submission already

[alpe]

As a group member I want to submit a proposal that is executed immediately when a ExecNow value is set and a sufficient number of group members have signed the message in order to ...?

Every signer must be part of the group. No duplicate signatures allowed. Every signer is considered a yes vote. Based on the decision policy configured the proposal will be executed or not.
Execution is an atomic operation so that it would either succeed or fail with the proposal creation.

Note:

• There is a gas cost per signature:
  • DefaultSigVerifyCostED25519 uint64 = 590
  • DefaultSigVerifyCostSecp256k1 uint64 = 1000
• There is a limit of max signatures allowed
  * DefaultTxSigLimit uint64 = 7