This PR is to improve builtins matching and type inference in SPIR-V
Backend. The model test case is printf call from OpenCL.std that has
several features allowing for a wider look at builtins support/type
inference:
(1) call in a "spirv-friendly" style (prefixed by __spirv_ocl_)
(2) restricted type of the 1st argument

Attached test cases checks several possible inputs. Support of the
extension SPV_EXT_relaxed_printf_string_address_space is to do (see:
https://github.com/KhronosGroup/SPIRV-Registry/blob/main/extensions/EXT/SPV_EXT_relaxed_printf_string_address_space.asciidoc).

This PR also fixes target ext type constants and
OpGroupAsyncCopy/OpGroupWaitEvents generation. A new test case is
attached.