perf callchain: Add a for_each callback style API

Add a for_each callback style API to callchain with
sample__for_each_callchain_node().

Possibly in the future such an API can avoid the overhead of
constructing the call chain list.

Signed-off-by: Ian Rogers <irogers@google.com>
Acked-by: Namhyung Kim <namhyung@kernel.org>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Casey Chen <cachen@purestorage.com>
Cc: Colin Ian King <colin.i.king@gmail.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Kan Liang <kan.liang@linux.intel.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Tom Zanussi <tzanussi@gmail.com>
Link: https://lore.kernel.org/r/20240812224119.744968-1-irogers@google.com


[ Split from a larger patch that introduced the API and use it ]
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>