[$] Inlining kfuncs into BPF programs

Eduard Zingerman presented a daring proposal that "makes sense if you thinkabout it a bit" at the 2025 Linux Storage, Filesystem,Memory-Management, and BPF Summit. He wants to inlineperformance-sensitive kernel functionsinto the BPF programs that call them. Hisprototype does not yet address all of the design problems inherent in that idea,but it did spark a lengthy discussion about the feasibility of his proposal.