aya/bpf
Tatsuyuki Ishi 41c6b56142 bpf: Replace map types to use &self, remove HashMap::get_mut
The bpf_map_defs are now wrapped with UnsafeCell, which also happens to
provide a cozy way to get a *mut pointer. An UnsafeCell isn't strictly
required as the struct fields are practically opaque to us, but using an
UnsafeCell follows the general best practices against miscompilation and
also prevents some obvious errors.

HashMap::get_mut was removed because the idea is completely unsound.
Previous users should wrap their data with UnsafeCell instead or use
atomics.

Closes: https://github.com/aya-rs/aya/issues/233
..
aya-bpf bpf: Replace map types to use &self, remove HashMap::get_mut
aya-bpf-bindings bpf: Remove generated getters
aya-bpf-cty bpf: Fix clippy warnings
aya-bpf-macros bpf: Support BPF_PROG_TYPE_SK_LOOKUP
Cargo.toml bpf: add aya-bpf-bindings