Use a struct/bitmap rather than a copied string from lexer.

In lexer give improved error message when too many precise flags are
given or repeated modifiers.

Before:

  $ perf stat -e 'cycles:kuk' true
  event syntax error: 'cycles:kuk'
                              \___ Bad modifier
  ...
  $ perf stat -e 'cycles:pppp' true
  event syntax error: 'cycles:pppp'
                              \___ Bad modifier
  ...
  $ perf stat -e '{instructions:p,cycles:pp}:pp' -a true
  event syntax error: '..cycles:pp}:pp'
                                    \___ Bad modifier
  ...

After:

  $ perf stat -e 'cycles:kuk' true
  event syntax error: 'cycles:kuk'
                                \___ Duplicate modifier 'k' (kernel)
  ...
  $ perf stat -e 'cycles:pppp' true
  event syntax error: 'cycles:pppp'
                                 \___ Maximum precise value is 3
  ...
  $ perf stat -e '{instructions:p,cycles:pp}:pp' true
  event syntax error: '..cycles:pp}:pp'
                                    \___ Maximum combined precise value is 3, adding precision to "cycles:pp"
  ...
Signed-off-by: Ian Rogers <irogers@google.com>
Reviewed-by: Kan Liang <kan.liang@linux.intel.com>
Tested-by: Atish Patra <atishp@rivosinc.com>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Beeman Strong <beeman@rivosinc.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>
Link: https://lore.kernel.org/r/20240416061533.921723-14-irogers@google.comSigned-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>