rtla/timerlat: Use pretty formatting only on interactive tty

rtla/timerlat: Use pretty formatting only on interactive tty

timerlat top does some background/font color formatting. While useful
on terminal, it breaks the output on other formats. For example, when
piping the output for pastebin tools, the format strings are printed
as characters. For instance:

  [2;37;40m                                     Timer Latency                                              [0;0;0m
    0 00:00:01   |          IRQ Timer Latency (us)        |         Thread Timer Latency (us)
  [2;30;47mCPU COUNT      |      cur       min       avg       max |      cur       min       avg       max[0;0;0m
    0 #1013      |        1         0         1        54 |        5         2         4        57
    1 #1013      |        3         0         1        10 |        6         2         4        15

To avoid this problem, do the formatting only if running on a tty,
and in !quiet mode.

Link: https://lkml.kernel.org/r/8288e1544ceab21557d5dda93a0f00339497c649.1713968967.git.bristot@kernel.org
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Juri Lelli <juri.lelli@redhat.com>
Signed-off-by: Daniel Bristot de Oliveira <bristot@kernel.org>