perf jevents: Add python converter script

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 <[email protected]>
Tested-by: John Garry <[email protected]>
Tested-by: Thomas Richter <[email protected]>
Tested-by: Xing Zhengjun <[email protected]>
Tested-by: Arnaldo Carvalho de Melo <[email protected]>
Cc: Alexander Shishkin <[email protected]>
Cc: Ananth Narayan <[email protected]>
Cc: Andi Kleen <[email protected]>
Cc: Andrew Kilroy <[email protected]>
Cc: Caleb Biggers <[email protected]>
Cc: Felix Fietkau <[email protected]>
Cc: Ingo Molnar <[email protected]>
Cc: James Clark <[email protected]>
Cc: Jiri Olsa <[email protected]>
Cc: Kajol Jain <[email protected]>
Cc: Kan Liang <[email protected]>
Cc: Kshipra Bopardikar <[email protected]>
Cc: Like Xu <[email protected]>
Cc: Mark Rutland <[email protected]>
Cc: Mathieu Poirier <[email protected]>
Cc: Namhyung Kim <[email protected]>
Cc: Nick Forrington <[email protected]>
Cc: Paul Clarke <[email protected]>
Cc: Perry Taylor <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: Qi Liu <[email protected]>
Cc: Ravi Bangoria <[email protected]>
Cc: Sandipan Das <[email protected]>
Cc: Santosh Shukla <[email protected]>
Cc: Stephane Eranian <[email protected]>
Cc: Will Deacon <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Arnaldo Carvalho de Melo <[email protected]>

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