bpftool: Use feature list in bash completion

Now that bpftool is able to produce a list of known program, map, attach
types, let's use as much of this as we can in the bash completion file,
so that we don't have to expand the list each time a new type is added
to the kernel.

Also update the relevant test script to remove some checks that are no
longer needed.

Signed-off-by: Quentin Monnet <quentin@isovalent.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Daniel Müller <deso@posteo.net>
Link: https://lore.kernel.org/bpf/20220629203637.138944-3-quentin@isovalent.com