Add support for pbtombstone executable

Added labeling and permissions for /system/bin/pbtombstone across various files, namely: plat_file_contexts_test, 202504.ignore.cil, and system_server.te. Updated file contexts and defined pbtombstone_exec as a system executable to ensure compatibility and proper execution.

Bug: 323857385
Flag: EXEMPT permissions update
Test: m && manual tests and permission check

Change-Id: I0d20366bb452f98d339dd413e074d5bd94b9549e
diff --git a/private/file_contexts b/private/file_contexts
index 7ef3226..ceebb07 100644
--- a/private/file_contexts
+++ b/private/file_contexts
@@ -353,6 +353,7 @@
 /system/bin/preopt2cachename u:object_r:preopt2cachename_exec:s0
 /system/bin/sgdisk      u:object_r:sgdisk_exec:s0
 /system/bin/blkid       u:object_r:blkid_exec:s0
+/system/bin/pbtombstone       u:object_r:pbtombstone_exec:s0
 /system/bin/flags_health_check -- u:object_r:flags_health_check_exec:s0
 /system/bin/idmap2(d)?              u:object_r:idmap_exec:s0
 /system/bin/update_engine           u:object_r:update_engine_exec:s0