[VPU] Added ConvertGather7ToGather1 pass to frontend (#7183)

This pr adds ConvertGather7ToGather1 pass to frontend before MergeGatherGatherElements pass, to make it so that when MergeGatherGatherElements is ran, any v7::Gather will be replaced with v1::Gather

inference-engine/src/vpu/graph_transformer/src/frontend/frontend.cpp

@@ -33,6 +33,7 @@
 #include <transformations/op_conversions/convert_minimum_to_power_and_max.hpp>
 #include <transformations/op_conversions/hswish_decomposition.hpp>
 #include <transformations/op_conversions/simplify_ctc_greedy_decoder_seq_len.hpp>
+#include <transformations/op_conversions/convert_gather_downgrade.hpp>
 #include <transformations/convert_precision.hpp>
 #include <legacy/transformations/convert_opset1_to_legacy/convert_opset1_to_legacy.hpp>
 #include <legacy/transformations/convert_opset1_to_legacy/convert_prior_to_ie_prior.hpp>
@@ -181,6 +182,7 @@ ie::CNNNetwork FrontEnd::convertNetwork(ie::CNNNetwork& network) {
     manager.register_pass<ngraph::pass::ConvertNMS1ToNMS5>();
     manager.register_pass<ngraph::pass::ConvertNMS3ToNMS5>();
     manager.register_pass<ngraph::pass::ConvertNMS4ToNMS5>();
+    manager.register_pass<ngraph::pass::ConvertGather7ToGather1>();
     manager.register_pass<vpu::MergeGatherGatherElements>();
     manager.register_pass<ngraph::pass::CommonOptimizations>();