Rework proposals to allow immediate execution for user-driven actions

[UMR1352]

Description

Rework proposals in order to make them always executable as soon as they are created if the controller that's creating them has enough voting power.

Motivation

When a controller that has enough voting power creates a proposal, the proposal gets executed right away. This is not the case for proposals that require users to drive them (send proposal, borrow proposal, controller execution proposal). This is not only annoying but it's also expensive fees-wise as it forces the user to run two transactions instead of just one.