Summary: A generic BPFTraceConnector class, plus a specific Derived class for grabbing CPU stats.

Test Plan: Currently using stirling_wrapper. Will look into whether a stand-alone test is possible.

Reviewers: kgandhi, zasgar, #engineering

Reviewed By: kgandhi, zasgar, #engineering

Subscribers: philkuz

Differential Revision: https://phab.corp.pixielabs.ai/D318

GitOrigin-RevId: 86bcd899e759df607eed7c199fae7716316ea595