support state override for debug_traceTransaction ("offchain events")

[hananbeer]

the debug_traceCall function supports state overrides, but debug_traceTransaction does not - it only accepts a transaction hash.

I wrote this originally as the backbone for generating "offchain events" (as developed by shadow / ghost logs)

to prevent confusion with nodes that don't implement this feature I created a distinct function debug_traceTransactionOverrides.
by overriding contracts bytecode it is possible to reexecute onchain transactions in different context, specifically to emit so called "offchain events" but not limited to this.

usage:

cast rpc debug_traceTransactionOverrides $txhash '{ "stateOverrides": { "$addr": { "code": "$bytecode" } } }'

eg for mainnet:

cast rpc debug_traceTransactionOverrides 0xc9ab90a1796613b0fbccb33827de583901d4c0775e89c0f25d604b7c3a71771e '{ "stateOverrides": { "0x0000001D0000F38CC10d0028474a9c180058B091": { "code": "0x6000ff" } } }' | jq .

note:
the format may differ a bit from other nodes (eg. in geth the keys ("stateOverride", "code") are case insensitive, in reth they are case sensitive)
this is unrelated to this patch.

see equivalent implementations:

geth: ethereum/go-ethereum#29423
erigon: erigontech/erigon#9847

[mattsse]

I think this is the same as adding support for overrides in debug_trace_transaction?

GethDebugTracingCallOptions contains two optional objects but is otherwise the same as GethDebugTracingOptions

so I think we can integrate this without breaking anything and avoid a new endpoint

[hananbeer]

it is, but as I mentioned this distinction is to avoid confusion.
also see this reply in my geth version:
ethereum/go-ethereum#29423 (comment)

it seems they support this within debug_traceCall (less convenient imo) but I've never seen this documented for any node before.

I want a standardized api across nodes, each node makes their own modifications and then things break when, for example, using load balancers across different providers.