[Snippets][Coverity] Fixed 139702 and 140933 (#25230)

### Details:
- *Fixed coverity issues: `Null pointer dereferences` and `Performance
inefficiencies`*

### Tickets:
 - *140933*
 - *139702*

Author: a-sidorova

src/common/snippets/include/snippets/lowered/loop_manager.hpp

@@ -102,7 +102,7 @@ class LoopManager {
                      bool set_default_handlers = true,
                      bool is_work_amount_const = false) {
         const auto normalized_increment = utils::is_dynamic_value(work_amount) || work_amount == 0 ? increment : std::min(increment, work_amount);
-        const auto handlers = set_default_handlers
+        const auto& handlers = set_default_handlers
                                   ? SpecificIterationHandlers(work_amount, normalized_increment)
                                   : SpecificIterationHandlers();
         const auto loop_info = std::make_shared<UnifiedLoopInfo>(work_amount, normalized_increment, entries, exits, handlers, is_work_amount_const);

src/common/snippets/src/lowered/loop_manager.cpp

@@ -123,7 +123,7 @@ std::pair<LinearIR::constExprIt, LinearIR::constExprIt> LoopManager::get_loop_bo
 }
 
 LoopPort LoopManager::get_loop_port_by_expr_port(const ExpressionPort& expr_port, const size_t loop_id) {
-    auto get_loop_port = [&](const std::vector<LoopPort>& ports) {
+    auto get_loop_port = [&](const std::vector<LoopPort>& ports) -> const LoopPort& {
         auto it = std::find_if(ports.cbegin(), ports.cend(), [&](const LoopPort& p) { return *p.expr_port == expr_port; });
         if (it == ports.cend())
             OPENVINO_THROW("Expression has not been found among loop ports. Loop id: " + std::to_string(loop_id));
@@ -272,7 +272,7 @@ void LoopManager::fuse_loops(LinearIR::constExprIt loop_begin_target, LinearIR::
     auto input_ports_upper = loop_info_upper->get_input_ports();
     auto output_ports_upper = loop_info_upper->get_output_ports();
     auto input_ports_lower = loop_info_lower->get_input_ports();
-    auto output_ports_lower = loop_info_lower->get_output_ports();
+    const auto& output_ports_lower = loop_info_lower->get_output_ports();
     fuse_loop_ports(output_ports_upper, input_ports_lower, loop_id_upper);
 
     const auto& from = fuse_into_upper ? loop_id_lower : loop_id_upper;
@@ -285,9 +285,9 @@ void LoopManager::fuse_loops(LinearIR::constExprIt loop_begin_target, LinearIR::
     const auto handlers = SpecificIterationHandlers::merge_handlers(loop_info_upper->get_handlers(), loop_info_lower->get_handlers());
     const auto is_work_amount_const = loop_info_upper->is_work_amount_const() || loop_info_lower->is_work_amount_const();
 
-    auto new_entries = input_ports_upper;
+    auto new_entries = std::move(input_ports_upper);
     new_entries.insert(new_entries.end(), input_ports_lower.begin(), input_ports_lower.end());
-    auto new_exits = output_ports_upper;
+    auto new_exits = std::move(output_ports_upper);
     new_exits.insert(new_exits.end(), output_ports_lower.begin(), output_ports_lower.end());
 
     m_map[to] = std::make_shared<UnifiedLoopInfo>(work_amount, increment, new_entries, new_exits, handlers, is_work_amount_const);

src/common/snippets/src/lowered/pass/validate_expanded_loops.cpp

@@ -52,7 +52,10 @@ void ValidateExpandedLoops::validate_loop_information(const LinearIR& linear_ir)
         const auto& expanded_loop_info = ov::as_type_ptr<ExpandedLoopInfo>(p.second);
         INFORMATIVE_ASSERT(expanded_loop_info, "expects only ExpandedLoopInfo in LoopManager");
 
-        if (expanded_loop_info->get_unified_loop_info() != current_unified_loop_info) {
+        const auto& unified_loop_info = expanded_loop_info->get_unified_loop_info();
+        INFORMATIVE_ASSERT(unified_loop_info, "expects non nullptr UnifiedLoopInfo in ExpandedLoopInfo");
+
+        if (unified_loop_info != current_unified_loop_info) {
             // If there is `current_unified_loop_info` - the previos loop is finished and need to validate total information
             if (current_unified_loop_info) {
                 INFORMATIVE_ASSERT(current_work_amount == current_unified_loop_info->get_work_amount(),
@@ -61,7 +64,7 @@ void ValidateExpandedLoops::validate_loop_information(const LinearIR& linear_ir)
                                    "total finalization offsets are not equal to finalization offsets of undefined loop");
             }
 
-            current_unified_loop_info = expanded_loop_info->get_unified_loop_info();
+            current_unified_loop_info = unified_loop_info;
 
             INFORMATIVE_ASSERT(current_unified_loop_info->get_input_count() == expanded_loop_info->get_input_count() &&
                                current_unified_loop_info->get_output_count() == expanded_loop_info->get_output_count(),
@@ -74,6 +77,7 @@ void ValidateExpandedLoops::validate_loop_information(const LinearIR& linear_ir)
         }
 
         current_work_amount = utils::dynamic_safe_add(current_work_amount, expanded_loop_info->get_work_amount());
+        INFORMATIVE_ASSERT(current_unified_loop_info, "expects non nullptr current UnifiedLoopInfo");
         INFORMATIVE_ASSERT(current_unified_loop_info->get_ptr_increments() == expanded_loop_info->get_ptr_increments(),
                            "incompatible pointer increments with UnifiedLoopInfo");