[OpenMP][OpenMPIRBuilder] Move copyInput to a passed in lambda function and...

[OpenMP][OpenMPIRBuilder] Move copyInput to a passed in lambda function and re-order kernel argument load/stores (#68124)

This patch moves the existing copyInput function
into a lambda argument that can be defined
by a caller to the function.

This allows more flexibility in how the function
is defined, allowing Clang and MLIR to utilise
their own respective functions and types inside
of the lamba without affecting the OMPIRBuilder
itself.

The idea is to eventually replace/build on
the existing copyInput function that's used
and moved into OpenMPToLLVMIRTranslation.cpp
to a slightly more complex implementation
that uses MLIRs map information (primarily
ByRef and ByCapture information at the
moment).

The patch also moves kernel load stores to the top
of the kernel, prior to the first openmp runtime 
invocation. Just makes the IR a little closer to Clang.