jevents.c is large, has a dependency on an old forked version of jsmn,
and is challenging to work upon. A lot of jevents.c's complexity comes
from needing to write json and csv parsing from first principles. In
contrast python has this functionality in standard libraries and is
already a build pre-requisite for tools like asciidoc (that builds all
of the perf man pages).

Introduce jevents.py that produces identical output to jevents.c. Add a
test that runs both converter tools and validates there are no output
differences. The test can be invoked with a phony build target like:

  $ make -C tools/perf jevents-py-test

The python code deliberately tries to replicate the behavior of
jevents.c so that the output matches and transitioning tools shouldn't
introduce regressions. In some cases the code isn't as elegant as hoped,
but fixing this can be done as follow up.

Committer testing:

  $ make -C tools/perf jevents-py-test
  make: Entering directory '/var/home/acme/git/perf/tools/perf'
    BUILD:   Doing 'make -j32' parallel build
    HOSTCC  fixdep.o
    HOSTLD  fixdep-in.o
    LINK    fixdep

  Auto-detecting system features:
  ...                         dwarf: [ on  ]
  ...            dwarf_getlocations: [ on  ]
  ...                         glibc: [ on  ]
  ...                        libbfd: [ on  ]
  ...                libbfd-buildid: [ on  ]
  ...                        libcap: [ on  ]
  ...                        libelf: [ on  ]
  ...                       libnuma: [ on  ]
  ...        numa_num_possible_cpus: [ on  ]
  ...                       libperl: [ on  ]
  ...                     libpython: [ on  ]
  ...                     libcrypto: [ OFF ]
  ...                     libunwind: [ on  ]
  ...            libdw-dwarf-unwind: [ on  ]
  ...                          zlib: [ on  ]
  ...                          lzma: [ on  ]
  ...                     get_cpuid: [ on  ]
  ...                           bpf: [ on  ]
  ...                        libaio: [ on  ]
  ...                       libzstd: [ on  ]
  ...        disassembler-four-args: [ on  ]

    HOSTCC  pmu-events/json.o
    HOSTCC  pmu-events/jsmn.o
    HOSTCC  pmu-events/jevents.o
    HOSTLD  pmu-events/jevents-in.o
    LINK    pmu-events/jevents
  Checking architecture: arm64
  Generating using jevents.c
  Generating using jevents.py
  Diffing
  Checking architecture: nds32
  Generating using jevents.c
  Generating using jevents.py
  Diffing
  Checking architecture: powerpc
  Generating using jevents.c
  Generating using jevents.py
  Diffing
  Checking architecture: s390
  Generating using jevents.c
  Generating using jevents.py
  Diffing
  Checking architecture: x86
  Generating using jevents.c
  Generating using jevents.py
  Diffing
  make: Leaving directory '/var/home/acme/git/perf/tools/perf'
  $
Signed-off-by: Ian Rogers <irogers@google.com>
Tested-by: John Garry <john.garry@huawei.com>
Tested-by: Thomas Richter <tmricht@linux.ibm.com>
Tested-by: Xing Zhengjun <zhengjun.xing@linux.intel.com>
Tested-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Ananth Narayan <ananth.narayan@amd.com>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: Andrew Kilroy <andrew.kilroy@arm.com>
Cc: Caleb Biggers <caleb.biggers@intel.com>
Cc: Felix Fietkau <nbd@nbd.name>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: James Clark <james.clark@arm.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Kajol Jain <kjain@linux.ibm.com>
Cc: Kan Liang <kan.liang@linux.intel.com>
Cc: Kshipra Bopardikar <kshipra.bopardikar@intel.com>
Cc: Like Xu <likexu@tencent.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Mathieu Poirier <mathieu.poirier@linaro.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Nick Forrington <nick.forrington@arm.com>
Cc: Paul Clarke <pc@us.ibm.com>
Cc: Perry Taylor <perry.taylor@intel.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Qi Liu <liuqi115@huawei.com>
Cc: Ravi Bangoria <ravi.bangoria@amd.com>
Cc: Sandipan Das <sandipan.das@amd.com>
Cc: Santosh Shukla <santosh.shukla@amd.com>
Cc: Stephane Eranian <eranian@google.com>
Cc: Will Deacon <will@kernel.org>
Link: https://lore.kernel.org/r/20220629182505.406269-3-irogers@google.comSigned-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>