[GPU] Update PagedAttention creation logic (#28802)

### Details:
- Currently GenAI library sets fully dynamic shapes for Key/Value cache
buffers, which causes GPU Plugin to fail during compile_model() call.
Therefore, update PagedAttention creation logic to use head_size and
heads_num parameters from the rt_info if available
- GenAI related PR:
openvinotoolkit/openvino.genai#1666

src/plugins/intel_gpu/src/plugin/ops/paged_attention.cpp

@@ -25,10 +25,16 @@ static void CreatePagedAttentionExtensionOp(ProgramBuilder& p, const std::shared
     auto inputs = p.GetInputInfo(op);
     auto prim = cldnn::paged_attention(layer_type_name_ID(op), inputs);
 
-    auto key_cache_ps = op->get_input_partial_shape(3);
+    const auto& rt_info = op->get_rt_info();
+    const auto k_head_size_id = "k_head_size";
+    const auto num_k_heads_id = "num_k_heads";
+    const auto has_rt_params = rt_info.find(k_head_size_id) != rt_info.end() &&
+                               rt_info.find(num_k_heads_id) != rt_info.end();
+
     auto query_ps = op->get_input_partial_shape(0);
-    auto head_size = key_cache_ps[2].get_length();
-    auto kv_heads_num = key_cache_ps[1].get_length();
+    auto key_cache_ps = op->get_input_partial_shape(3);
+    auto head_size = has_rt_params ? rt_info.at(k_head_size_id).as<int64_t>() : key_cache_ps[2].get_length();
+    auto kv_heads_num = has_rt_params ? rt_info.at(num_k_heads_id).as<int64_t>() : key_cache_ps[1].get_length();
 
     // WA: in some cases, the query input may have a bounded dimension
     // Use input shape of the input node in such cases