[bitcoin-wallet-snap] Add support for `keyring_createAccounts`

# Description

As part of the performance improvements around account management, the keyring API now supports a new method to allow the creation of multiple accounts in one request via the method `keyring_createAccounts` (`@metamask/keyring-api` version 22.0.0), this new RPC method accepts a batch request — either a single BIP-44 index or an inclusive index range — and creates all accounts in one call.

This ticket requires the Bitcoin snap to also support the method `keyring_createAccounts` and update the clients configuration to enable account creation batching. To do so, go to the file `controller-init/multichain/multichain-account-service-init.ts` (extension client case) and update the Bitcoin provider configuration to set `createAccounts > batched` to `true`

# Acceptance Criteria

1. The Bitcoin snap now supports `keyring_createAccounts`
2. A new version is released and both clients are updated to use it
3. Set the `createAccounts > batched` configuration value to `true` in both clients

# References

- Solana snap PR: https://github.com/MetaMask/snap-solana-wallet/pull/599
- [Method signature](https://github.com/MetaMask/accounts/blob/8488a657c5daf6203d1c59ca80081f54d03a77fb/packages/keyring-api/src/api/keyring.ts#L71)

Start with the Bitcoin snap's existing keyring methods and the linked keyring_createAccounts signature, then compare the Solana snap PR. Inspect controller-init/multichain/multichain-account-service-init.ts for the extension client and locate the corresponding configuration for the other client. Done means the Bitcoin snap supports the method, a new version is released, and both clients enable batched account creation.

Written by the indexing model from the issue text.