[clang] [HLSL] Add __is_scalarized_layout_compatible (PR #102227)

[Damyan Pepper via cfe-commits]

damyanp wrote:

> HLSL tends to rely pretty aggressively on scalarization occuring in the complier, which allows for some relaxed language behaviors when types are fully sclarized to equivalent scalar representations.

Some typos:

* occuring --> occurring
* complier --> compiler
* sclarized --> scalarized

https://github.com/llvm/llvm-project/pull/102227