Redirect pallets weights generated by benchmarking in runtime.

[hbulgarini]

Once we have the weights files generated from the benchmarking bot, the pallets configured in the Trappist runtime should be redirected to use the weights that are created under the runtime/trappist/weights folder instead of using the weights crate from the pallets.

Here is an example:

Before:

impl pallet_treasury::Config for Runtime {
         ...
	type BurnDestination = ();
	type MaxApprovals = MaxApprovals;
	type WeightInfo = pallet_treasury::weights::SubstrateWeight<Runtime>;
         ...
}

After:

mod weights;

impl pallet_treasury::Config for Runtime {
         ...
	type BurnDestination = ();
	type MaxApprovals = MaxApprovals;
	type WeightInfo = weights::pallet_treasury::SubstrateWeight<Runtime>;
         ...
}

Depends on #141
CC: @kalaninja