LRUCache assert was triggered during disagg tests

Bug Report

[2025/05/21 05:24:13.169 +08:00] [FATAL] [LRUCache.h:376] ["Assert current_weight < (1ull << 63) fail! LRUCache became inconsistent. There must be a bug in it."] [source=Fatal] [thread_id=16]
[2025/05/21 05:24:13.192 +08:00] [ERROR] [BaseDaemon.cpp:355] ["(from thread 16) Terminate called after throwing an instance of DB::Exception
Code: 0, e.displayText() = DB::Exception: Assert current_weight < (1ull << 63) fail! LRUCache became inconsistent. There must be a bug in it., e.what() = DB::Exception
Stack trace:
  0x56085a6a3b06        terminate_handler() [tiflash+133139206]
                        dbms/src/Common/StackTrace.cpp:23
  0x7fb7ad60b473        std::__terminate(void (*)()) [libc++abi.so.1+226419]
  0x7fb7ad60b428        std::terminate() [libc++abi.so.1+226344]
  0x560855ca1e21        void DB::exception_details::logAndTerminate<char const*&>(char const*, int, char const*, std::__1::shared_ptr<DB::Logger> const&, char const*&) [tiflash+55537185]
  0x560855ca187b        void DB::exception_details::logAndTerminate<>(char const*, int, char const*, char const*) [tiflash+55535739]
  0x56085a63c0aa        DB::LRUCache<DB::DM::Remote::RNMVCCIndexCache::CacheKey, DB::DM::Remote::RNMVCCIndexCache::CacheValue, DB::DM::Remote::RNMVCCIndexCache::CacheKeyHasher, DB::DM::Remote::RNMVCCIndexCache::CacheValueWeight>:"] [source=BaseDaemon] [thread_id=1066]
[2025/05/21 05:24:13.192 +08:00] [ERROR] [BaseDaemon.cpp:364] [########################################] [source=BaseDaemon] [thread_id=1066]
[2025/05/21 05:24:13.192 +08:00] [ERROR] [BaseDaemon.cpp:365] ["(from thread 16) Received signal Aborted(6)."] [source=BaseDaemon] [thread_id=1066]

Start by reproducing the disagg tests and inspect LRUCache.h at line 376, where the assertion is reported. Trace the RNMVCCIndexCache entry in the stack trace to identify the cause; done means the assertion no longer aborts the disagg tests and the failure has regression coverage.