tools/intel_gpu_top: Add support for stdout logging

Two new output modes are added: listing of text data to standard out (-l
on the command line), and dumping of JSON formatted records (-J), also to
standard out.

The first mode is selected automatically when non-interactive standard out
is detected.

Example of text output:

 Freq MHz      IRQ RC6 Power     IMC MiB/s           RCS/0           BCS/0           VCS/0           VCS/1          VECS/0
 req  act       /s   %     W     rd     wr       %  se  wa       %  se  wa       %  se  wa       %  se  wa       %  se  wa
   0    0        0   0  0.00    360      0    0.00   0   0    0.00   0   0    0.00   0   0    0.00   0   0    0.00   0   0
 350  350        0 100  0.00     35      2    0.00   0   0    0.00   0   0    0.00   0   0    0.00   0   0    0.00   0   0
 350  350        0 100  0.00     34      2    0.00   0   0    0.00   0   0    0.00   0   0    0.00   0   0    0.00   0   0
 350  350        0 100  0.00    143      6    0.00   0   0    0.00   0   0    0.00   0   0    0.00   0   0    0.00   0   0
 350  350        0 100  0.00    169      7    0.00   0   0    0.00   0   0    0.00   0   0    0.00   0   0    0.00   0   0
 350  350        0 100  0.00    169      7    0.00   0   0    0.00   0   0    0.00   0   0    0.00   0   0    0.00   0   0

Example of JSON output:

{
        "period": {
                "duration": 1002.525224,
                "unit": "ms"
        },
        "frequency": {
                "requested": 349.118398,
                "actual": 349.118398,
                "unit": "MHz"
        },
        "interrupts": {
                "count": 0.000000,
                "unit": "irq/s"
        },
        "rc6": {
                "value": 99.897752,
                "unit": "%"
        },
        "power": {
                "value": 0.000000,
                "unit": "W"
        },
        "imc-bandwidth": {
                "reads": 149.683843,
                "writes": 6.104093,
                "unit": "MiB/s"
        },
        "engines": {
                "Render/3D/0": {
                        "busy": 0.000000,
                        "sema": 0.000000,
                        "wait": 0.000000,
                        "unit": "%"
                },
                "Blitter/0": {
                        "busy": 0.000000,
                        "sema": 0.000000,
                        "wait": 0.000000,
                        "unit": "%"
                },
                "Video/0": {
                        "busy": 0.000000,
                        "sema": 0.000000,
                        "wait": 0.000000,
                        "unit": "%"
                },
                "Video/1": {
                        "busy": 0.000000,
                        "sema": 0.000000,
                        "wait": 0.000000,
                        "unit": "%"
                },
                "VideoEnhance/0": {
                        "busy": 0.000000,
                        "sema": 0.000000,
                        "wait": 0.000000,
                        "unit": "%"
                }
        }
}

v2:
 * Show example output in commit message.
 * Install signal handler to complete output on SIGINT. (Chris Wilson)

v3:
 * Use asprintf where possible. (Chris Wilson)

v4:
 * Check asprintf return value, not the pointer.
 * Rename fmt_d/dd to fmt_width/precision. (Chris Wilson)

Signed-off-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
References: https://bugs.freedesktop.org/show_bug.cgi?id=108689


Cc: Eero Tamminen <eero.t.tamminen@intel.com>
Cc: 3.14pi@ukr.net
Cc: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>