refactor: Replace WeightSubmitter with bittensor_rs::Subtensor

Major simplification of weight submission using Subtensor API directly:

- Remove WeightSubmitter wrapper, use bittensor_rs::Subtensor
- Subtensor handles commit-reveal automatically:
  - CRv4: Timelock encryption (chain auto-reveals)
  - Legacy: Hash commit-reveal with persistence
  - Direct: When commit-reveal disabled
- State persistence via Subtensor::with_persistence()
- Automatic reveal of pending commits on restart
- Re-export BittensorSigner, ExtrinsicWait from platform-bittensor

Update bittensor-rs to b5720eb with new query methods:
- get_current_epoch(netuid)
- get_mechanism_count(netuid)
- get_current_phase(netuid)
- is_in_reveal_phase(netuid)
- pending_commits_info()

Author: EchoBT

Cargo.lock

@@ -30,7 +30,7 @@ license = "Apache-2.0"
 
 [workspace.dependencies]
 # Bittensor (with CRv4 timelock encryption support and new Subtensor API)
-bittensor-rs = { git = "https://github.com/CortexLM/bittensor-rs", rev = "0614e74" }
+bittensor-rs = { git = "https://github.com/CortexLM/bittensor-rs", rev = "b5720eb" }
 
 # Async runtime
 tokio = { version = "1.40", features = ["full", "sync", "macros", "rt-multi-thread"] }