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.te b/private/file.te
index 3a66143..6bdcc39 100644
--- a/private/file.te
+++ b/private/file.te
@@ -192,6 +192,9 @@
 # /sys/firmware/acpi/tables
 type sysfs_firmware_acpi_tables, fs_type, sysfs_type;
 
+# Type for /system/bin/pbtombstone.
+type pbtombstone_exec, system_file_type, exec_type, file_type;
+
 # Allow files to be created in their appropriate filesystems.
 allow fs_type self:filesystem associate;
 allow cgroup tmpfs:filesystem associate;