Implement nonce fix tool to fill mempool nonce gaps

[sudo-shashank]

Summary

Lotus provides lotus-shed noncefix to recover from nonce gaps in the message pool: when pending messages skip nonces (e.g. after a stuck or dropped message), later sends fail with “nonce too low” / the address stays blocked until the gap is filled.

Forest has no equivalent. Users can query the next nonce (forest-cli mpool nonce) but cannot automatically fill gaps like Lotus.

Background / Lotus reference:
Command: lotus-shed noncefix
Source: https://github.com/filecoin-project/lotus/blob/master/cmd/lotus-shed/nonce-fix.go

NAME:
   lotus-shed noncefix

USAGE:
   lotus-shed noncefix [command options]

OPTIONS:
   --start value        (default: 0)
   --end value          (default: 0)
   --addr value         
   --auto               (default: false)
   --gas-fee-cap value  specify gas fee cap for nonce filling messages (default: 0)
   --help, -h           show help

Use case: Unblock an address when the mpool has a nonce hole between chain state and the next pending message.

Completion Criteria

• CLI fills nonce gaps for an address when --auto detects a gap between chain nonce and lowest pending nonce.
• Manual --start / --end mode works when --auto is not set
• Integration test

Additional Links & Resources