`polkadot-parachain-primitives` should not depend on `frame-support`. (#1897)

This PR does not make any functional changes to the code. Rather, it
restructures the dependency graph.

Before this PR, the crate `polkadot-parachain-primitives` depended
directly on the crate `frame-support`. This is wrong in principal
because a parachain does not necessarily have anything to do with frame.

This dependency was only for the `Weight` type which was just a
re-export from `sp-weights` anyway. So this PR changes the dependency to
be directly on the much lighter `sp-weights`.

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Co-authored-by: Joshy Orndorff <[email protected]>
Co-authored-by: command-bot <>