selftests/bpf: Migrate all deprecated perf_buffer uses

Migrate all old-style perf_buffer__new() and perf_buffer__new_raw()
calls to new v1.0+ variants.

Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20211111053624.190580-7-andrii@kernel.org