advisory discover: cache NVD API query results

[luhring]

Querying NVD's API is expensive. Even in the best case, where the user has an API key, we can only make requests at ~1.7 reqs/sec. And today Wolfi has ~1400 package definitions according to wolfictl ls.

NVD's response data for a given request (CPE) is unlikely to change frequently. We should consider caching API responses locally for some duration of time (e.g. 24 hours). This would greatly speed up the total runtime of the wolfictl advisory discover command.

And meanwhile, even with cached data, we would still be able to:

• Detect new matches using cached data, e.g. when a new version stream is added
• Detect new matches using uncached data for newly added distro packages