[clang] [clang-cl] Add support for [[msvc::constexpr]] C++11 attribute (PR #71300)

[Richard Dzenis via cfe-commits]

RIscRIpt wrote:

> Also, please don't 'force-push', just push an additional commit to your review. It erases history and makes reviewing it about 3x harder since history/context gets lost.

Sorry. I did this, because I am used to such workflow and reviewing [range-diff](https://github.com/llvm/llvm-project/compare/c700d21baf395aafbeea88778d13188650ed0c21..1af977ae49616ee00a64f50302f4cd88f9a51881); but to make it work one have to follow strict rule of pushing changes and rebased branch separately (which I failed to do previous time).

https://github.com/llvm/llvm-project/pull/71300