Fix Rocky Linux 8 ASAN plugin test failures (#12675)

Add leak suppression for ld-linux-x86-64.so to fix false positive memory
leak reports on Rocky Linux 8 when running plugin tests with ASAN enabled.

The tests properly call dlclose() for each dlopen(), but ASAN's instrumentation
of the dynamic linker reports false positive leaks during plugin initialization.

Fixes: test_PluginDso, test_PluginFactory, test_RemapPluginInfo on Rocky Linux 8

Author: bryancall

src/proxy/http/remap/unit-tests/remap_test_dlopen_leak_suppression.txt

@@ -23,4 +23,7 @@
 # something nasty or ASAN is detecting a false-positive.
 # PluginDso::load
 leak:PluginDso::load
-leak:call_init
+leak:call_init
+# On Rocky Linux 8, ASAN reports leaks from the dynamic linker during dlopen
+# These are false positives as we properly call dlclose for each dlopen
+leak:ld-linux-x86-64.so