Fix GPU tests after new dead code pass

[jabraham17]

Fixes a few GPU tests after adding a new dead code pass in #27562.

These tests use empty functions to trigger certain conditions in the compiler, but the empty functions are now being removed. This is a test only fix to make those functions not be empty.

• Tested that all failing tests now pass with CHPL_GPU=nvidia

test/gpu/native/assertOnFailToGpuizeAttr.chpl
test/gpu/native/assertOnNotGpuEligible.chpl
test/gpu/native/errors/gpuTrace.chpl
test/gpu/native/errors/gpuTraceStd.chpl
test/gpu/native/errors/gpuTraceViaCall.chpl
test/gpu/native/reportGpu.chpl

[Reviewed by @e-kayrakli]