Set -Werror=braced-scalar-init (#86911)
- `vector<T>({0})` would give you the vector(size, ...) ctor and produce an empty vector of T, along with the scalar-init warning
- `vector<T>({T(0)})` would give you the vector of a single T(0) as you might have intended, and bypasses the warning/error
- the warning can easily be missed but can have serious consequences, so make it an error
Pull Request resolved: https://github.com/pytorch/pytorch/pull/86911
Approved by: https://github.com/albanD
