perf script: Cache the output type

perf script: Cache the output type

Right now every time we need to figure out the type of an evsel for
output purposes we do a quick sequence of ifs, but there are new cases
where there is a need to do more complex iterations over multiple data
structures, sso allow for caching this operation on a hole of 'struct
evsel'.

This should really be done on the evsel->priv area that 'perf script'
sets up, but more work is needed to make sure that it is allocated when
we need it, right now it is only used for conditionally, add some
comments so that we move this to that 'perf script' specific area when
the conditions are in place for that.

Acked-by: Thomas Falcon <thomas.falcon@intel.com>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Ian Rogers <irogers@google.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: James Clark <james.clark@linaro.org>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Kan Liang <kan.liang@linux.intel.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Ravi Bangoria <ravi.bangoria@amd.com>
Link: https://lore.kernel.org/lkml/Z2XCi3PgstSrV0SE@x1
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>