Vesting should not fund extrinsic inclusion fees

[bedeho]

In the interest of simplifying the relevance of locks being able to pay for various costs associated with transactions, which ideally should not be the invite lock, we need to remove the ability of having funds subject to vesting constraint be able to fund extrinsic inclusion fees. Currently this is the functionality of the vesting pallet we use, which comes with the FRAME suite.

We have two alternatives

1. forking vesting pallet and making lock configurable: we likely could get this merged back into upstream even, but lets not depend on that!
2. use alternative vesting pallets, e.g. from orml

┆Issue is synchronized with this Asana task by Unito

[bedeho]

We are going with 1.