Add functions to check ABI of eBPF collection

[lmb]

It's useful to do some basic checks on a Collection if there is a user space component. Basically,
let the user specific a list of MapSpec and make sure that they are present in the collection and have the right types. The same goes for ProgramSpec.

Open question: how to do this for pinned collections? In that case we do not have *Spec to work with.

[nathanjsweet]

I think if the user wants it they need to give an additional path to save metadata to (I know that the bpffs supports this in later kernels, but it would probably be good to have something backwards compatible to avoid confusion).

[nathanjsweet]

Let's get some unsupported errors going for some of these syscalls.

[lmb]

The only bit of the ABI that relies on syscalls being available are the LoadPinned* functions. I'll add some code which returns not supported.