[CI] Improved benchmark outputs

[Dinonard]

Description

There are two distinct benchmark outputs we want to generate.

The first one is related for the "standalone" pallet benchmark which should generate WeightInfo trait and define SubstrateWeight struct with impl of the aforementioned trait, as well as default impl on the empty tuple.

The second output type is specific to the runtime where only SubstrateWeight with impl of the already defined trait is needed.

Running benchmarks in our CI should generate both as two separate files.

[Dinonard]

Can be done relatively easily.