[$] Simplifying the BPF verifier

The BPF verifier is a complex program. This has the unfortunate effect of makingit simultaneously more difficult for contributors to work on, and more likelyto harbor unknown bugs. Shung-Hsi Yu had two concrete proposals for how tosimplify the verifier to make it easier to maintain that he presented at the 2024Linux Storage,Filesystem, Memory Management, and BPF Summit. Yu proposed changing how theverifier tracks partially known values and cleaning up the interface tohide the details of the value-tracker's internal representation.