Update Polkadot extrinsic encoding to support new spec for Acala

[doom]

Description

How to test

Types of changes

Checklist

• Create pull request as draft initially, unless its complete.
• Add tests to cover changes as needed.
• Update documentation as needed.
• If there is a related Issue, mention it in the description.

If you're adding a new blockchain

• I have read the guidelines for adding a new blockchain.

[github-actions]

Binary size comparison

➡️ aarch64-apple-ios: 12.29 MB

➡️ aarch64-apple-ios-sim: 12.29 MB

➡️ aarch64-linux-android: 15.80 MB

➡️ armv7-linux-androideabi: 13.48 MB

➡️ wasm32-unknown-emscripten: 11.20 MB

[JaimeToca]

Successful simulation

curl --location 'https://acala-api.twnodes.com/transaction/fee-estimate' \
--header 'Content-Type: application/json' \
--data '{"tx":"0x45028400e9590e4d99264a14a85e21e69537e4a64f66a875d38cb8f76b305f41fabe24a900a9c3111fb98507f929e4da9aea30f996c69d2790e5a1e789f91634dc5d4f6afb155e0f1ea623498c04778f06dbc698109c3490c3e6b4c33d8e58ebab82a0f40bd5020000000a0000c8c602ded977c56076ae38d98026fa669ca10d6a2b5a0bfc4086ae7668ed1c60070010a5d4e8"}
'

[rkokhatskyi]

Looks good, fix verified:

https://acala.subscan.io/extrinsic/0xced905e73e1cce51854c6452fae5513828d80a110e1ed6e86dfee745dfaf2203

https://acala.subscan.io/extrinsic/0x4ca90d6498a749eb24f533d613ada188035d631623c7de077b35a7b0aea3ff08