[DirectX] Add API to find a resource binding given a use of a resource

[bogner]

There are times when we need to determine what unique resource we have given a use of a resource type (such as #114130). The full scope of doing this is tracked in #125126, but the entire scope of that task isn't practical until we support heap and library resources.

In the meantime, we should implement an API in DXIL resource analysis that, given a Value * that is a use of a resource type, walks defs until it finds a call to the llvm.dx.resource.handlefrombinding intrinsic and looks up that binding in the DXILBindingMap. The expectation is that this API would be trivially modifiable with the more generic resource lookup once #125126 is done.