AssetHub Referenda Support for Polkadot and Kusama

[eugypalu]

Adds support for submitting referenda on both Polkadot and Kusama AssetHub networks, while maintaining full compatibility with relay chain submissions. Updates include new CLI flags and logic to handle AssetHub submissions.

Partially resolves #36. Full resolution will be completed with #42

[ggwpez]

Need this now, will try it for Kusama 1.9.2 upgrade.

[ggwpez]

Not sure if it uses the correct runtime. I tried it but all Calls only decode on RC, not AH.

> opengov-cli submit-referendum \
    --proposal "./upgrade-kusama-1.9.2/kusama-1.9.2.call" \
    --network "kusama" --track "root" --asset-hub --output CallData

No enactment time specified. Defaulting to `After(10)`.
Specify an enactment time with `--at <block>` or `--after <blocks>`.


Submit the preimage for the public referendum:
0x20007501180408630004000100a10f04082f00000602022b94360110880009ee6d70c902e426f11890146bbbb3da440cf45e49240f525f0cece9e9be1fcc6c0009d905ea233b779dfae428febc319661bbcc0ee861dcec336d18e5a3dc6ee667f6

Open a public referendum to dispatch the call:
0x15000000021d55c8d9634a8bfbf22adf7e082f1ef333f3b56820d459804003c6b3d85470615d000000010a000000

Batch to submit on Kusama Relay Chain:
0x18040820007501180408630004000100a10f04082f00000602022b94360110880009ee6d70c902e426f11890146bbbb3da440cf45e49240f525f0cece9e9be1fcc6c0009d905ea233b779dfae428febc319661bbcc0ee861dcec336d18e5a3dc6ee667f615000000021d55c8d9634a8bfbf22adf7e082f1ef333f3b56820d459804003c6b3d85470615d000000010a000000