Node 14 is quite long in the tooth at this point, and hasn't been
supported by this module's engines declaration for a long time.

Thanks to @logaretm for helping get this started.

This is a first pass, but it significantly expands the coverage of
`LRUCache.Status` objects, as well as hooking them into a metrics
channel for sync operations and a set of tracingChannels for async
operations.

One thing that's lacking currently, but maybe not important, is knowing
_which_ cache an operation is related to, if there is more than one
cache in use. If you're just interested in overall age of cached items,
time spent fetching, whatever, it's probably fine, but if someone asks,
we could conceivably put a `status.cache = this` field on the status
object, which would solve the problem.

Performance impact seems minimal, as long as it's not used (ha), but
it doesn't seem meaningfully worse than just using status objects in the
first place, so likely the perf impact is dominated by just "creating
and disposing of a bunch of short-lived objects".

Tracing channels and metrics are added unconditionally in CommonJS, and
using a dynamic import with top level await in ESM. Since CommonJS is
pretty much strictly Node.js at this point, this should enable any other
platforms to use the observability features if they support them, or
else just get a dummy object that says `{ hasSubscribers: false }`, thus
preventing it from ever being used.