[Relay, Tests] Make expressions in the DynamicToStatic pass tests more dynamic

[jtuyls]

While experimenting with dyn.strided_slice I noticed that some of the DynamicToStatic pass tests are not testing dynamic expressions. For example, the created strided_slice function here

tvm/tests/python/relay/test_pass_dynamic_to_static.py

Line 435 in 02f885a

func = relay.Function([x], z)

looks like this:

fn (%x: Tensor[(1, 3, 10, 10), float32]) {
  strided_slice(%x, begin=[0, 0, 0, 0], end=[1, 3, 10, 10], strides=[1, 1, 1, 1], axes=None)
}

which I think doesn't test the DynamicToStatic pass being executed on this expression. With the small changes in this PR, the above function looks like this:

fn (%x: Tensor[(1, 3, 10, 10), float32], %begin: Tensor[(4), int64], %end: Tensor[(4), int64], %strides: Tensor[(4), int64]) {
  %0 = cast_like(0, %begin);
  %1 = shape_of(%x, dtype="int32");
  %2 = cast_like(%1, %begin);
  %3 = slice_like(%2, %begin, axes=None);
  %4 = less(%begin, %0);
  %5 = add(%begin, %3);
  %6 = where(%4, %5, %begin);
  %7 = greater_equal(%6, %3);
  %8 = where(%7, %3, %6);
  dyn.strided_slice(%x, %8, %end, %strides, begin=None, end=None, strides=None, axes=None)
}

which I think is a better test for the DynamicToStatic pass.

Similarly, tests for topk, resize2d, upsampling, upsampling3d and pad have been adjusted.

@mbrookhart Could you help with reviewing this PR?

[mbrookhart]

LGTM! Thanks

I think about six months ago (after these tests were written), I went back and added code to ops like relay.op.strided_slice to check the inputs for Constant-ness and return the static op if they were constant. I must have forgotten to check these tests to ensure they remained dynamic. Thank you!