bpf: Remove Input interface and simply use bytes as the input.

[copybara-service]

bpf: Remove Input interface and simply use bytes as the input.

This removes the interface indirection from BPF evaluation, which is
a very hot path (runs for every application syscall for seccomp'd containers)
and simplifies the code in general.

            │   initial   │         hey_look_no_interfaces         │
            │   sec/op    │   sec/op     vs base                   │
Interpreter   26.31n ± 0%   21.12n ± 0%  -19.73% (p=0.000 n=21+20)