Behaviour for funding a Relay deposit by broadcasting an on-chain token transfer to the Riddler-managed deposit address (the "B" backstop, used when the gasless pull is unavailable; see axol-io/Riddler#120).
raxol's Wallet signs but does not broadcast, and the proven EVM transaction
stack (EIP-1559 signing, RLP, nonce, JSON-RPC submit) lives in raxol_acp,
which depends on this package. So rather than duplicate fund-moving transaction
code here, the deposit broadcast is injected: a caller that can see that stack
supplies a module implementing this behaviour, and ExecuteRelayTransfer uses
it when present.
Implementations must be idempotent on transfer_id: a retried call for the
same logical transfer must not double-send.
Summary
Callbacks
Broadcast a token transfer of amount_atomic of token to the deposit address
to on chain_id. Returns the source-chain transaction hash.