Optimize MuxInspector

[mattsse]

Currently the muxtracer uses several instances of TracingInspector

however the return frame handler of GethBuilder dont consume the the type:

https://github.com/paradigmxyz/evm-inspectors/blob/aad9b3cc9920997a29c9e5034b78b8866627f739/src/tracing/builder/geth.rs#L117-L117

This means the mux tracer can be optimized so that only 1 instance per tracer (fourbyte,TracingInspector) is used:

https://github.com/paradigmxyz/evm-inspectors/blob/aad9b3cc9920997a29c9e5034b78b8866627f739/src/tracing/mux.rs#L170-L170

This way we should also get rid of the dangerous recursive MuxInspector variant

https://github.com/paradigmxyz/evm-inspectors/blob/aad9b3cc9920997a29c9e5034b78b8866627f739/src/tracing/mux.rs#L173-L173

TODO

switch from an enum approach to an Option<FourByteInspector> Option<TransactionInspector> approach that are then reused when the MuxFrame is populated

fyi @ArtificialPB

[ArtificialPB]

Do you want to completely disallow mux tracer nesting? If you want to trace both prestate and poststate (aka prestate tracer in diff mode), the only way to do it right now is to nest a muxTracer (tracer name is a map key in the config).

Agree with other points about reusing the tracer instances. I can take this, ~mid next week most likely. I'll also finish the JS tracer support