bpftool: Split FEATURE_TESTS/FEATURE_DISPLAY definitions in Makefile

bpftool: Split FEATURE_TESTS/FEATURE_DISPLAY definitions in Makefile

Make FEATURE_TESTS and FEATURE_DISPLAY easier to read and less likely to
be subject to conflicts on updates by having one feature per line.

Suggested-by: Andres Freund <andres@anarazel.de>
Signed-off-by: Quentin Monnet <quentin@isovalent.com>
Tested-by: Niklas Söderlund <niklas.soderlund@corigine.com>
Acked-by: Song Liu <song@kernel.org>
Link: https://lore.kernel.org/r/20221025150329.97371-4-quentin@isovalent.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>