## Why this should be merged
Adds logging of `libevm` modification of default behaviour.
## How this works
1. Introduces `log.Lazy` functions to allow expensive logging operations
to be computed i.f.f. required by the logging level.
2. Adds `Info` logging for registration of types and `Debug` logging for
all else.
3. Only paths that change behaviour in a potentially unpredictable
manner are logged; of note, RLP / JSON encoding is _not_ considered
unpredictable given that registered extras are logged.
4. The minimal viable package, `set`, was necessary because we don't
want to depend on `avalanchego` and the `hashicorp/go-set` latest
version requires a later version of Go. #153 tracks a swap to the latter
when possible.
The `eth/tracers/internal/tracetest` test flaked at least twice
(unrelated to these changes) so I've marked it as such since it's not
worth a separate PR.
## How this was tested
New unit test on `log.Lazy` + `set` methods. Existing CI for the rest as
it's a refactor.
