PPMemoryAllocationsTest.PPMacroDefinesAllocations fails under AddressSanitizer

The test `PPMemoryAllocationsTest.PPMacroDefinesAllocations` in `clang/unittests/Lex/PPMemoryAllocationsTest.cpp` fails when building with `-DLLVM_USE_SANITIZER='Address'`:

```
Preprocessor allocator memory for 1000000 #define: 136839168
Bytes per #define: 1.368392e+02
clang/unittests/Lex/PPMemoryAllocationsTest.cpp:92: Failure
Expected: (BytesPerDefine) < (130.0f), actual: 136.839172 vs 130
```

It looks like the test asserts that per #define memory usage stays below 130 bytes. Under ASAN, the BumpPtrAllocator adds a red zone to every allocation (controlled by RedZoneSize). This inflates total slab memory from approx 120 to approx 137 bytes per define, exceeding the threshold.

This was introduced in https://github.com/llvm/llvm-project/pull/205711 which restructured RedZoneSize gating. The commit message states the test was validated at "120.06 B/define". It looks like that measurement was done without ASAN. Leading to a bug.

I propose to add something like:
```
#if LLVM_ADDRESS_SANITIZER_BUILD
// ASAN red zones add overhead to each bump-ptr allocation within the slab.
EXPECT_LT(BytesPerDefine, 140.0f);
#else
EXPECT_LT(BytesPerDefine, 130.0f);
#endif
```

Start in clang/unittests/Lex/PPMemoryAllocationsTest.cpp at PPMemoryAllocationsTest.PPMacroDefinesAllocations and compare the existing expectation with normal and AddressSanitizer builds. Update the sanitizer-specific allocation bound described in the issue, then run this test in both configurations and confirm each reports passing results.

Written by the indexing model from the issue text.