feat: treasury executor role

[shenshin]

What

• Create Executor role for the Treasury contract
• Treasury is now deployed along with other DAO contracts within the Governor module
• The Timelock is assigned the Executor role for the Treasury in the deployment script following deployment.
• Make use of the Executor role in the tests

Why

The Treasury contract should have two distinct roles: Default Admin and Executor, instead of just the Default Admin role as it was before. The Default Admin role is assigned to the deployer, whose function is to manage the assignment of other roles. Ideally, only the deployer should have this role.

The Executor role is assigned to the Timelock contract, which will execute Governor proposals, and only it will be able to call the withdraw functions. The Admin should not have the ability to withdraw funds, as that is not part of its function.

The Treasury contract is now deployed after the other contracts within the same module, as it is necessary to call the grantRole function post-deployment to assign the Executor role to the Timelock.