[Profiler] Don't assign in AppendOnlyList::emplace_back (#85716)
It turns out that we're invoking the copy assign operator in AppendOnlyList. While copy elision is expected to mostly hide any costs it does present issues for types with deleted copy assign operators. (It also seems to produce slightly worse assembly: https://godbolt.org/z/o4Gvz1fKs)
Calling new at the correct position seems to be a better way to go about this. (At least from looking at other high performance containers like SmallVector.)
Differential Revision: [D39852804](https://our.internmc.facebook.com/intern/diff/D39852804/)
Pull Request resolved: https://github.com/pytorch/pytorch/pull/85716
Approved by: https://github.com/chaekit
