CW-1103:Token Validation Issues (#2327)

* feat(token_validation): Improve flow for adding new tokens across wallets

This change:
- Implements check to see if a token is already added, preventing duplicates
- Triggers dialog warning if its a duplicate token
- Takes EVM Chains contract adddress case-insensitivity when making checks for potential scams.

* refactor(token_validation): Modify token management flow

This change:
- Removes duplicate token check during token addition in EVMChainWalletBase.
- Introduces a flag to indicate if a token is being edited
- Adjusts token addition validation to bypass checks when editing an existing token.

* Update lib/src/screens/dashboard/edit_token_page.dart

---------

Co-authored-by: Omar Hatem <omarh.ismail1@gmail.com>

lib/solana/cw_solana.dart

@@ -155,4 +155,10 @@ class CWSolana extends Solana {
   List<String> getDefaultTokenContractAddresses() {
     return DefaultSPLTokens().initialSPLTokens.map((e) => e.mintAddress).toList();
   }
+
+  @override
+  bool isTokenAlreadyAdded(WalletBase wallet, String contractAddress) {
+    final solanaWallet = wallet as SolanaWallet;
+    return solanaWallet.splTokenCurrencies.any((element) => element.mintAddress == contractAddress);
+  }
 }