OpenGov in Westend and Rococo (#1177)

Migrating [PR from the archived polkadot
repo](https://github.com/paritytech/polkadot/pull/7272)

As per
https://github.com/paritytech/polkadot/pull/7272#issuecomment-1559240466,
the changes in this MR include the following pallets into [x] Rococo and
[x] Westend runtimes:

    pallet_conviction_voting
    pallet_referenda
    pallet_ranked_collective
    pallet_custom_origins
    pallet_whitelist

And only for westend-runtime:

    pallet_treasury

Following [Kusama runtime
config](https://github.com/paritytech/polkadot/tree/dbae30efe080a1d41fe54ef4da8af47614c9ca93/runtime/kusama/src)
as a baseline.

Benchmarking of the following pallets done for both Rococo and Westend:

    pallet_conviction_voting
    pallet_referenda
    pallet_ranked_collective (only on Rococo)
    pallet_whitelist

And only for Westend:

    pallet_treasury

Removed Gov1 from Rococo as in
https://github.com/paritytech/polkadot/pull/6701

Rococo Gov1 storage will be cleaned in a different PR - [issue ](https://github.com/paritytech/polkadot-sdk/issues/1618

)

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Co-authored-by: Giles Cope <[email protected]>