Consider exposing Builder::attrs publically

[Phantomical]

This crate doesn't cover the entire surface of the perf_event_open API and with things like dynamic PMUs it's not really possible for it to cover all use cases. It would be nice if Builder::attrs was exposed publically so that downstream crates could modify them directly.

[jimblandy]

As an unsafe method, sure.

[PoignardAzur]

Seconded. Being able to pass a custom value to attrs.config would be super helpful.

Not sure it would need to be unsafe, though. Unsafe implies "there are certain invariants you need to uphold to make sure your code is sound", but in this case I don't see what the invariants would be.