btf: move wire type definitions into sys

[lmb]

btf_types.go contains a bunch of hand written structs that map to types defined in the kernel's UAPI. We should replace these with auto generated types in sys package and use those from btf. This guarantees that we match the kernel 1:1 and also ensures that there is no implicit padding present.

• btfType
• btfEnum
• btfArray
• btfMember
• btfParam
• btfVar
• btfVarSecInfo
• btfDeclTag
• btfEnum64

The changes need to be made here: https://github.com/cilium/ebpf/blob/0acd95c6c83cabeff32e94594cd4b7de6e7df4a2/internal/cmd/gentypes/main.go#L157-L208

[amiremohamadi]

I see bunch of helper functions and methods in btf_types.go. are we gonna keep them inside that file and just auto generate the structs inside sys package?

@lmb

[lmb]

We could move those into a separate file in sys. That way we can have manually written methods on auto generated types.