Context

This PR introduces a new pallet-based architecture for creating GenericCall objects without immediate submission. This is an intermediate step toward full Proxy pallet support, which requires the ability to compose nested calls where one GenericCall is passed as a parameter to another.

Changes

• New CallBuilder base class: Provides a unified interface for creating GenericCall instances from any Subtensor pallet.
• Pallet implementations: Added factory classes for Balances, Crowdloan, Sudo, SubtensorModule, Swap, and Commitments.
• Unified async/sync support: All pallets work seamlessly with both Subtensor and AsyncSubtensor instances.
• Refactored extrinsics: Updated transfer and start_call extrinsics to use the new pallet architecture.

Benefits

• No code duplication: GenericCall objects can be created once and reused for fee estimation, submission, or nesting in other calls.
• Type safety: Methods return Union[GenericCall, Awaitable[GenericCall]] based on the subtensor type.
• Backward compatible: Existing extrinsic functions continue to work unchanged.
• Extensible: New pallets can be easily added by extending CallBuilder.
• The entire SDK API is backward compatible.
• All builder methods are implemented consistently with Subtensor functions.

Example Usage

Create a sync call without submitting

subtensor = bt.Subtensor("local")
call = SubtensorModule(subtensor).start_call(netuid=14)

Create a async call without submitting

async_subtensor = bt.AsyncSubtensor("local")
call = await SubtensorModule(async_subtensor).start_call(netuid=14)

Use for fee estimation

fee = subtensor.get_extrinsic_fee(call, wallet.coldkeypub)

Submit the call

response = subtensor.sign_and_send_extrinsic(call=call, wallet=wallet)

Nest calls (preparation for Proxy support)

inner_call = SubtensorModule(subtensor).start_call(netuid=14)
sudo_call = Sudo(subtensor).sudo(call=inner_call)
response = subtensor.sign_and_send_extrinsic(call=sudo_call, wallet=wallet)

Dynamic call creation within defined pallet class

call = SubtensorModule(subtensor, dynamic_function=True).burned_register(
    netuid=14, 
    hotkey=alice_wallet.hotkey.ss58_address,
)
response = subtensor.sign_and_send_extrinsic(call=call, wallet=wallet)

Dynamic call creation without defined pallet class

call = CallBuilder(subtensor, dynamic_function=True).create_composed_call(
    call_module="SubtensorModule",
    call_function="burned_register",
    netuid=14, 
    hotkey=alice_wallet.hotkey.ss58_address,
)
response = subtensor.sign_and_send_extrinsic(call=call, wallet=wallet)

Testing

• All existing e2e tests pass. The implementation has been validated with both sync and async subtensor instances.
• Added e2e tests with dynamically created call.