[BUG] Get wrong measure time in graph debug runtime

[jcf94]

This bug was introduced in #6964 .
Currently, use graph debug runtime will get wrong time result.

Cause:

tvm/src/runtime/graph/debug/graph_runtime_debug.cc

Lines 150 to 159 in d052752

	double RunOpHost(int index) {
	auto op_tbegin = std::chrono::high_resolution_clock::now();
	op_execs_[index]();
	const TVMContext& ctx = data_entry_[entry_id(index, 0)]->ctx;
	TVMSynchronize(ctx.device_type, ctx.device_id, nullptr);
	auto op_tend = std::chrono::high_resolution_clock::now();
	double op_duration =
	std::chrono::duration_cast<std::chrono::duration<double> >(op_tend - op_tbegin).count();
	return op_duration;
	}

This function returns a time with second, but is expected to return microsecond.

cc @areusch

[junrushao]

I suppose the bug has been fixed by #7197, is that correct?

[areusch]

no, it was tangential to that PR, so this issue is open to track a follow-on to fix