[SP004]: Implement the translation from initialize list to constructor with visibility control

[kaizhangNV]

This task is tracking the implementation of one topic in the design proposal of https://github.com/shader-slang/slang/blob/master/docs/proposals/004-initialization.md.

If a struct is initialized with initialize list, we will need to synthesize a constructor, and translate the initialize list to the call to such synthesized constructor.