[LifetimeSafety] False positive after adding to an std::vector

The following code produces a false positive lifetime warning about `vec` being invalidated after `push_back()`. Same goes for `emplace_back()`.
```cpp
void repro(std::vector& vec)
{
vec.push_back(1);
vec[0] = 2;
}
```

Compiled with `-std=c++20 -Wlifetime-safety-invalidation`

```
:3:12: warning: parameter 'vec' is later invalidated [-Wlifetime-safety-invalidation]
3 | void repro(std::vector& vec)
| ^~~~~~~~~~~~~~~~~~~~~
:5:9: note: parameter 'vec' is invalidated here
5 | vec.push_back(1);
| ~~~~^~~~~~~~~~~~
:6:5: note: later used here
6 | vec[0] = 2;
| ^~~
```

Here is the code on godbolt: https://godbolt.org/z/xvrfo7rj6
This issue appeared with 23.1.0 and still exists in 23.1.1.

```
clang version 23.1.1 (https://github.com/llvm/llvm-project 6dfe1677ab8dffbc6ec13d53a1e0215d75147689)
Target: x86_64-pc-windows-msvc
Thread model: posix
Build config: +alloc:rpmalloc
```

Start with the provided std::vector repro and run Clang with -std=c++20 -Wlifetime-safety-invalidation, comparing push_back() and emplace_back(). Trace the lifetime-safety invalidation handling for vector mutation and add or update coverage for this case; done means the false warning is gone while genuine invalidation warnings remain.

Written by the indexing model from the issue text.