Add Acc debugging functionality similar to Debug.Trace

[ivogabe]

Description

To make it easier to debug Accelerate programs, this PR adds functionality to inspect intermediate values of a computation, similar to what Debug.Trace provides for Haskell programs. This is the accompanying change of AccelerateHS/accelerate#485.

Motivation and context

This change makes it easier to debug Accelerate programs, which has been requested often.

How has this been tested?

I've tested this in my Delta stepping implementation, on the native and PTX backend.

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)

Checklist:

• My code follows the code style of this project.
• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I have added tests to cover my changes.
• All new and existing tests passed.

[tomsmeding]

I like how you manage to reuse atraceOp from the interpreter here in the backend. Looks nice, simple.