Add CombineTransforms operator

[jantonguirao]

Why we need this PR?

Pick one, remove the rest

• It adds new feature needed to combine several affine transforms into one

What happened in this PR?

Fill relevant points, put NA otherwise. Replace anything inside []

• What solution was applied:
  Added a new operator CombineTransforms
• Affected modules and functionalities:
  New op
• Key points relevant for the review:
  New op implementation
• Validation and testing:
  Python tests
• Documentation (including examples):
  Docstr

JIRA TASK: [DALI-1626]

[mzient]

Suggested change

	DALI_SCHEMA(CombineTransforms)
	DALI_SCHEMA(TransformCombine)

I know that "combine transforms" is how you'd say it in English, we'll likely end up with "transforms.Combine" anyway

[JanuszL]

Suggested change

	.NumInput(2, 10)
	.NumInput(2, 99)

[JanuszL]

Suggested change

	in0_shape, " and ", shape, "."));
	in0_shape, " and ", shape, " for ", i, " input.".));

[JanuszL]

Suggested change

	std::iota(input_order_.begin(), input_order_.end(), 0);
	if (!reverse_order_) {
	std::reverse(input_order_.begin(), input_order_.end()); // descending order
	}
	if (!reverse_order_) {
	std::iota(input_order_.rbegin(), input_order_.rend(), 0);
	} else {
	std::iota(input_order_.begin(), input_order_.end(), 0);
	}

[mzient]

I think it would be better to swap nesting order. Also, I think that this input_order_ is too much.

[mzient]

Suggested change

	mat = next_mat * mat; // mat mul
	mat = reverse_ ? mat * next_mat : next_mat * mat; // mat mul

This obviates the need for input_order_ and the condition should not pose too much overhead. With reversed loop nesting order, mat could be a local variable that's stored immediately in the output (no need for matrices).

[mzient]

The last row is never changed, so this can be hoisted outside the loop over inputs.

[mzient]

Maybe we should get these views ones to some vector/smallvector? Now it will involve far too many of vector allocations and copies. Sorry, I haven't noticed that problem when I first suggested reversing the nesting order.

[mzient]

Use emplace only when converting.

Suggested change

	in_views.emplace_back(view<T, 2>(in));
	in_views.push_back(view<T, 2>(in));

[jantonguirao]

!build

[dali-automaton]

CI MESSAGE: [1682089]: BUILD STARTED

[dali-automaton]

CI MESSAGE: [1682089]: BUILD PASSED