Use `Cow<'static, str>` for opcode string

[DaniPopes]

This op.to_string() is a significant waste of time and memory because op.as_str() returns a &'static str

revm-inspectors/src/tracing/types.rs

Line 655 in 424ca99

op: self.op.to_string(),

It can be avoided if the field was a Cow<'static, str> here https://github.com/alloy-rs/alloy/blob/566cee40c4413f2fb921bbbea705c45f4eb25d9a/crates/rpc-types-trace/src/geth/mod.rs#L75-L76

@mattsse however this would be a breaking change in alloy, wdyt?

[mattsse]

moving this to the 2.0 milestone