perf annotate: Introduce annotated_source__get_line()

perf annotate: Introduce annotated_source__get_line()

It's a helper function to get annotation_line at the given offset
without using the offsets array.  The goal is to get rid of the
offsets array altogether.  It just does the linear search but I
think it's better to save memory as it won't be called in a hot
path.

Signed-off-by: Namhyung Kim <namhyung@kernel.org>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Ian Rogers <irogers@google.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Kan Liang <kan.liang@linux.intel.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: https://lore.kernel.org/r/20240404175716.1225482-4-namhyung@kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>