[ov::Symbol] get rid of self pointing for root symbol (openvinotoolkit#24137)

### Details:
 - *gets rid of self-pointing for root symbol*

Co-authored-by: Michal Lukaszewski <michal.lukaszewski@intel.com>

Author: jane-intel

src/core/include/openvino/core/symbol.hpp

@@ -24,18 +24,14 @@ std::shared_ptr<Symbol> OPENVINO_API ancestor_of(const std::shared_ptr<Symbol>&
 /// \brief Class representing unique symbol for the purpose of symbolic shape inference. Equality of symbols is being
 /// tracked by Disjoint-set data structure
 /// \ingroup ov_model_cpp_api
-class OPENVINO_API Symbol : public std::enable_shared_from_this<Symbol> {
+class OPENVINO_API Symbol {
 public:
     /// \brief Default constructs a unique symbol
     Symbol() = default;
 
 private:
-    /// \brief Returns immediate parent of the Symbol, in case parent is unknown sets this as a parent for itself
-    std::shared_ptr<Symbol> parent();
-
     friend std::shared_ptr<Symbol> ov::symbol::ancestor_of(const std::shared_ptr<Symbol>& x);
     friend void ov::symbol::set_equal(const std::shared_ptr<Symbol>& lhs, const std::shared_ptr<Symbol>& rhs);
-    friend bool ov::symbol::are_equal(const std::shared_ptr<Symbol>& lhs, const std::shared_ptr<Symbol>& rhs);
 
     std::shared_ptr<Symbol> m_parent = nullptr;
 };

src/core/src/symbol.cpp

@@ -6,9 +6,10 @@
 
 std::shared_ptr<ov::Symbol> ov::symbol::ancestor_of(const std::shared_ptr<Symbol>& symbol) {
     auto x = symbol;
-    while (x->parent().get() != x.get()) {
-        x->m_parent = x->parent()->parent();
-        x = x->parent();
+    while (x->m_parent) {
+        if (x->m_parent->m_parent)
+            x->m_parent = x->m_parent->m_parent;
+        x = x->m_parent;
     }
     return x;
 }
@@ -27,9 +28,3 @@ void ov::symbol::set_equal(const std::shared_ptr<Symbol>& lhs, const std::shared
         return;  // already are equal
     lhs_root->m_parent = rhs_root;
 }
-
-std::shared_ptr<ov::Symbol> ov::Symbol::parent() {
-    if (!m_parent)
-        m_parent = shared_from_this();
-    return m_parent;
-}