perf tools: Add 'evlist' control command

Add a new 'evlist' control command to display all the evlist events.
When it is received, perf will scan and print current evlist into perf
record terminal.

The interface string for control file is:

  evlist [-v|-g|-F]

The syntax follows perf evlist command:
  -F  Show just the sample frequency used for each event.
  -v  Show all fields.
  -g  Show event group information.

Example session:

  terminal 1:
    # mkfifo control ack
    # perf record --control=fifo:control,ack -e '{cycles,instructions}'

  terminal 2:
    # echo evlist > control

  terminal 1:
    cycles
    instructions
    dummy:HG

  terminal 2:
    # echo 'evlist -v' > control

  terminal 1:
    cycles: size: 120, { sample_period, sample_freq }: 4000, sample_type:            \
    IP|TID|TIME|ID|CPU|PERIOD, read_format: ID, disabled: 1, inherit: 1, freq: 1,    \
    sample_id_all: 1, exclude_guest: 1
    instructions: size: 120, config: 0x1, { sample_period, sample_freq }: 4000,      \
    sample_type: IP|TID|TIME|ID|CPU|PERIOD, read_format: ID, inherit: 1, freq: 1,    \
    sample_id_all: 1, exclude_guest: 1
    dummy:HG: type: 1, size: 120, config: 0x9, { sample_period, sample_freq }: 4000, \
    sample_type: IP|TID|TIME|ID|CPU|PERIOD, read_format: ID, inherit: 1, mmap: 1,    \
    comm: 1, freq: 1, task: 1, sample_id_all: 1, mmap2: 1, comm_exec: 1, ksymbol: 1, \
     bpf_event: 1

  terminal 2:
    # echo 'evlist -g' > control

  terminal 1:
    {cycles,instructions}
    dummy:HG

  terminal 2:
    # echo 'evlist -F' > control

  terminal 1:
    cycles: sample_freq=4000
    instructions: sample_freq=4000
    dummy:HG: sample_freq=4000

This new evlist command is handy to get real event names when
wildcards are used.

Adding evsel_fprintf.c object to python/perf.so build, because
it's now evlist.c dependency.

Adding PYTHON_PERF define for python/perf.so compilation, so we
can use it to compile in only evsel__fprintf from evsel_fprintf.c
object.

Signed-off-by: Jiri Olsa <jolsa@kernel.org>
Tested-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Acked-by: Namhyung Kim <namhyung@kernel.org>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Alexei Budankov <abudankov@huawei.com>
Cc: Ian Rogers <irogers@google.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Michael Petlan <mpetlan@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephane Eranian <eranian@google.com>
Link: http://lore.kernel.org/lkml/20201226232038.390883-3-jolsa@kernel.org


Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>