dt: disable core dumps in crash tracker tests

I chose to set the core_pattern as it is the most reliable and simplest
option for our current setup.

Note that in our current CDT setup, core dumps are not written to a file
directly by the kernel but instead use a piping mechanism where they
pipe the coredump to `apport`. Because of this, the RLIMIT_CORE of the
process (set through ulimit) is not respected, meaning ulimit alone
cannot disable core dumps.

For reference, see the "Piping core dumps to a program" section of
https://www.man7.org/linux/man-pages/man5/core.5.html

tests/rptest/tests/crash_loop_checks_test.py

@@ -57,6 +57,9 @@ def __init__(self, test_context):
         )
         self.broker = self.redpanda.nodes[0]
 
+        # Disable core dumps as they take a long time (>1min). Core dumps are uninteresting for this test, since this test intentionally trigger crashes.
+        self.broker.account.ssh("sysctl -w kernel.core_pattern='|/dev/null'")
+
     def remove_crash_loop_tracker_file(self, broker):
         broker.account.ssh(
             f"rm -f {CrashLoopChecksTest.CRASH_LOOP_TRACKER_FILE}")