perf parse-events: Name the two term enums

perf parse-events: Name the two term enums

Name the enums used by 'struct parse_events_term' to
parse_events__term_val_type and parse_events__term_type.

This allows greater compile time error checking.

Fix -Wswitch related issues by explicitly listing all enum values prior
to default.

Add config_term_name to safely look up a parse_events__term_type name,
bounds checking the array access first.

Add documentation to 'struct parse_events_terms' and reorder to save
space.

Signed-off-by: Ian Rogers <irogers@google.com>
Tested-by: Kan Liang <kan.liang@linux.intel.com>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: James Clark <james.clark@arm.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Rob Herring <robh@kernel.org>
Link: https://lore.kernel.org/r/20230831071421.2201358-3-irogers@google.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>