[llvm] [SPIR-V] Expose an API call to initialize SPIRV target and translate input LLVM IR module to SPIR-V (PR #107216)

[Vyacheslav Levytskyy via llvm-commits]

https://github.com/VyacheslavLevytskyy ready_for_review https://github.com/llvm/llvm-project/pull/107216