fix(build): fix /Z7 /Zi conflict in Debug on Windows

[JalinWang]

Problem

Windows Debug/RelWithDebInfo builds emit thousands of warnings:

What Happens

1. What the top-level CMakeLists.txt did. Get /Z7 by string-replacing /Zi inside the config flag variables:

string(REPLACE "/Zi" "/Z7" _flags "${CMAKE_${_lang}_FLAGS_${_cfg}}")

2. But there is no /Zi in those variables — the replace is a no-op:

CMAKE_CXX_FLAGS_DEBUG:STRING=/Ob0 /Od /RTC1

3. Why. We require CMake 3.26, so CMP0141=NEW. Since CMake 3.25 the debug information format is no longer part of CMAKE_<LANG>_FLAGS_<CONFIG>; it is driven by CMAKE_MSVC_DEBUG_INFORMATION_FORMAT (default ProgramDatabase = /Zi) and appended near the end of the compile command — note the dash form -Zi, emitted next to -MTd, which is exactly how CMake's flag abstractions are written.

4. Result. Every TU gets /Z7 early and -Zi late (build_/d/compile_commands.json):

... /Ob0 /Od /RTC1  /Od /Z7   /W4  -MTd -Zi  /wd4251 ...
                          ^ from antlr4.windows.patch    ^ appended by CMake

cl : Command line warning D9025 : overriding '/Z7' with '/Zi', repeated across every
module that either got a /Zi→/Z7 patch or hardcodes /Z7:
thirdparty/antlr/antlr4.windows.patch, rocksdb-8.1.1/CMakeLists.txt#L189,
googletest internal_utils.cmake#L75.

MSVC applies the last flag, so /Zi wins — including for our own sources:

src/core/.../kmeans_cluster.cc: ... /Ob0 /Od /RTC1 -std:c++17 -MTd -Zi /utf-8 ...

So Debug/RelWithDebInfo builds were still producing per-target compile-time .pdb
files, while Release — the config CI builds — was not affected the same way: MSVC Release flags
carry no /Zi.

Fix

• Drive the format through the documented abstraction: CMAKE_MSVC_DEBUG_INFORMATION_FORMAT = "$<$<CONFIG:Debug,RelWithDebInfo>:Embedded>".
• set(CMAKE_POLICY_DEFAULT_CMP0141 NEW) before project(), so thirdparty subdirectories declaring an older cmake_minimum_required honour it too.
• Remove the dead string-replace loop.