[clang-tools-extra] [clang-tidy] Add `readability-redundant-zero-initializer` (PR #209367)

[Zeyi Xu via cfe-commits]

https://github.com/zeyi2 commented:

For this case:

```cpp
#include <vector>

std::vector<int> make() {
  return {0};
}
```

Currently the check would rewrite it to:

```cpp
std::vector<int> make() {
  return {};
}
```

IMO there is a semantic change here.

By looking at the AST dump:

```
`-CXXConstructExpr 0x9e2d6d6d8 <col:10, col:12> 'std::vector<int>' 'void (initializer_list<value_type>)' list std::initializer_list
        `-CXXStdInitializerListExpr 0x9e2d6d260 <col:10, col:12> 'initializer_list<value_type>':'std::initializer_list<int>'
          `-MaterializeTemporaryExpr 0x9e2d6d248 <col:10, col:12> 'const value_type[1]' xvalue
            `-InitListExpr 0x9e2d6d200 <col:10, col:12> 'const value_type[1]'
              `-IntegerLiteral 0x9e2d6c270 <col:11> 'int' 0
```

I think we should also filter `cxxStdInitializerListExpr()` in the matcher, something like: `unless(hasAncestor(cxxStdInitializerListExpr()))`

https://github.com/llvm/llvm-project/pull/209367