[scudo] Adjust PROT_MTE page count for secondary allocator (#192202) Secondary allocator currently mmaps 4 pages as PROT_MTE in case MTE is enabled in the allocator for Aarch64. Since only the headers are tagged, this is unnecessary, two pages are sufficient in worst case scenario. GitOrigin-RevId: 8c10815313231c629999a3f54b48f80eb6715e94