Expose rancher/lasso controller metrics

[brandond]

Lasso has some internal metrics around controller execution counts and durations, cache sizes, and so on. We should expose these so that we can better evaluate the performance of wrangler(lasso) controllers embedded in the K3s supervisor.

Ref: https://github.com/rancher/lasso/blob/f16ff2c25dc3291877b17af086fbcad7607fb390/pkg/metrics/metrics.go#L26-L49