perf pmu: Add and use legacy_terms in alias information

perf pmu: Add and use legacy_terms in alias information

Add support to finding/adding events from the default_core event
table. If an event already exists from sysfs/json then the
default_core configuration is saved in the legacy_terms string. Lazily
use the legacy_terms string to set a legacy hardware or cache event as
deprecated if the core PMU doesn't support it. Use the legacy terms
string to set the alternate_hw_config, avoiding the value needing to
be passed from the parse_events parser.

Tested-by: Thomas Richter <tmricht@linux.ibm.com>
Signed-off-by: Ian Rogers <irogers@google.com>
Tested-by: James Clark <james.clark@linaro.org>
Signed-off-by: Namhyung Kim <namhyung@kernel.org>