[TRANSFORMATIONS] Fix Optional to match even with no inputs

The Optional pattern type may create a wrong pattern to match
if no inputs are provided to the Optional node. If no inputs
present to the Optional type, it will not create an alternative
branch(es) to check against resulting in the incorrect matching.

Fix that by adding a check for the number of inputs being 0.

Do a minor refactoring/renaming for the readibility purposes.

Signed-off-by: Andrii Staikov <andrii.staikov@intel.com>

src/core/src/pattern/op/optional.cpp

@@ -15,11 +15,16 @@ std::vector<ov::DiscreteTypeInfo> ov::pass::pattern::op::Optional::get_optional_
 bool ov::pass::pattern::op::Optional::match_value(Matcher* matcher,
                                                   const Output<Node>& pattern_value,
                                                   const Output<Node>& graph_value) {
-    ov::OutputVector or_in_values = input_values();
-    auto wrap_node = std::make_shared<ov::pass::pattern::op::WrapType>(optional_types, m_predicate, or_in_values);
-    or_in_values.push_back(wrap_node);
+    // Turn the Optional node into WrapType node to create a case where the Optional node is present
+    ov::OutputVector input_values_to_optional = input_values();
+    size_t num_input_values_to_optional = input_values_to_optional.size();
+    auto wrap_node = std::make_shared<ov::pass::pattern::op::WrapType>(optional_types, m_predicate, input_values_to_optional);
 
-    if (matcher->match_value(std::make_shared<ov::pass::pattern::op::Or>(or_in_values), graph_value)) {
+    // Add the newly created WrapType node to the list containing its inputs and create an Or node with the list
+    input_values_to_optional.push_back(wrap_node);
+    auto or_node = std::make_shared<ov::pass::pattern::op::Or>(input_values_to_optional);
+
+    if (matcher->match_value(or_node, graph_value) || num_input_values_to_optional == 0) {
         auto& pattern_map = matcher->get_pattern_value_map();
         if (pattern_map.count(wrap_node)) {
             pattern_map[shared_from_this()] = graph_value;