Andrew Werner 628b7fb022 aya::programs::uprobe: add support for cookies
Fixes .

Note that this change does not add support in the public API for kprobes
or tracepoints, but it's a trivial matter of plumbing.

Along the way, the Uprobe::attach API is cleaned up to make the
attachment location more coherent. The logic being: if we're going to be
breaking the API anyway, may as well clean it up a bit.

Furthermore, the aya::sys::bpf_link_attach function is cleaned up by
properly modeling the the union in the final field with a rust enum.
..
tests aya::programs::uprobe: add support for cookies
lib.rs aya::programs::uprobe: add support for cookies
tests.rs aya::programs::uprobe: add support for cookies
utils.rs aya,integration-test: improve integration tests for info API