perf tools: Improve handling of hybrid PMUs in perf_event_attr__fprintf

Support the PMU name from the legacy hardware and hw_cache PMU
extended types.  Remove some macros and make variables more intention
revealing, rather than just being called "value".

Before:
```
$ perf stat -vv -e instructions true
...
------------------------------------------------------------
perf_event_attr:
  type                             0 (PERF_TYPE_HARDWARE)
  size                             136
  config                           0xa00000001
  sample_type                      IDENTIFIER
  read_format                      TOTAL_TIME_ENABLED|TOTAL_TIME_RUNNING
  disabled                         1
  inherit                          1
  enable_on_exec                   1
  exclude_guest                    1
------------------------------------------------------------
sys_perf_event_open: pid 181636  cpu -1  group_fd -1  flags 0x8 = 5
------------------------------------------------------------
perf_event_attr:
  type                             0 (PERF_TYPE_HARDWARE)
  size                             136
  config                           0x400000001
  sample_type                      IDENTIFIER
  read_format                      TOTAL_TIME_ENABLED|TOTAL_TIME_RUNNING
  disabled                         1
  inherit                          1
  enable_on_exec                   1
  exclude_guest                    1
------------------------------------------------------------
sys_perf_event_open: pid 181636  cpu -1  group_fd -1  flags 0x8 = 6
...
```

After:
```
$ perf stat -vv -e instructions true
...
------------------------------------------------------------
perf_event_attr:
  type                             0 (PERF_TYPE_HARDWARE)
  size                             136
  config                           0xa00000001 (cpu_atom/PERF_COUNT_HW_INSTRUCTIONS/)
  sample_type                      IDENTIFIER
  read_format                      TOTAL_TIME_ENABLED|TOTAL_TIME_RUNNING
  disabled                         1
  inherit                          1
  enable_on_exec                   1
------------------------------------------------------------
sys_perf_event_open: pid 181724  cpu -1  group_fd -1  flags 0x8 = 5
------------------------------------------------------------
perf_event_attr:
  type                             0 (PERF_TYPE_HARDWARE)
  size                             136
  config                           0x400000001 (cpu_core/PERF_COUNT_HW_INSTRUCTIONS/)
  sample_type                      IDENTIFIER
  read_format                      TOTAL_TIME_ENABLED|TOTAL_TIME_RUNNING
  disabled                         1
  inherit                          1
  enable_on_exec                   1
------------------------------------------------------------
sys_perf_event_open: pid 181724  cpu -1  group_fd -1  flags 0x8 = 6
...
```

Signed-off-by: Ian Rogers <irogers@google.com>
Reviewed-by: James Clark <james.clark@linaro.org>
Tested-by: Thomas Falcon <thomas.falcon@intel.com>
Tested-by: James Clark <james.clark@linaro.org>
Link: https://lore.kernel.org/r/20250307023906.1135613-1-irogers@google.com


Signed-off-by: Namhyung Kim <namhyung@kernel.org>