selftests/mm: run_vmtests: remove sudo and conform to tap

Remove sudo as some test running environments may not have sudo available.
Instead skip the test if root privileges aren't available in the test.

[usama.anjum@collabora.com: on-fault-limit: run test without root privileges otherwise skip]
  Link: https://lkml.kernel.org/r/20240201130538.1404897-1-usama.anjum@collabora.com
Link: https://lkml.kernel.org/r/20240125154608.720072-3-usama.anjum@collabora.com
Signed-off-by: Muhammad Usama Anjum <usama.anjum@collabora.com>
Cc: Ryan Roberts <ryan.roberts@arm.com>
Cc: Shuah Khan <shuah@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>