- the meaning of packed structs changed in zig 0.10. adjust accordingly.
  Use "extern struct" for the cases that directly map to C structs.

- Add new type info kinds, like enum64 and DeclTag

- change the Type enum to use the canonical names from libbpf.
  This is more predictable when comparing with external BPF
  documentation (than invented synonyms that need to be guessed)