perf bpf filter: Give terms their own enum

perf bpf filter: Give terms their own enum

Give the term types their own enum so that additional terms can be
added that don't correspond to a PERF_SAMPLE_xx flag. The term values
are numerically ascending rather than bit field positions, this means
they need translating to a PERF_SAMPLE_xx bit field in certain places
using a shift.

Signed-off-by: Ian Rogers <irogers@google.com>
Acked-by: Namhyung Kim <namhyung@kernel.org>
Cc: John Fastabend <john.fastabend@gmail.com>
Cc: Changbin Du <changbin.du@huawei.com>
Cc: Yang Jihong <yangjihong1@huawei.com>
Cc: Andrii Nakryiko <andrii@kernel.org>
Cc: bpf@vger.kernel.org
Signed-off-by: Namhyung Kim <namhyung@kernel.org>
Link: https://lore.kernel.org/r/20240524205227.244375-2-irogers@google.com