wallet: Remove Verify and IsLoaded methods

Checks are now consolidated in MakeBerkeleyDatabase function instead of
happening in higher level code.

This commit does not change behavior except for error messages which now
include more complete information.

src/wallet/walletdb.cpp

@@ -1032,11 +1032,6 @@ std::unique_ptr<WalletDatabase> MakeDatabase(const fs::path& path, const Databas
     return MakeBerkeleyDatabase(path, options, status, error);
 }
 
-bool IsWalletLoaded(const fs::path& wallet_path)
-{
-    return IsBDBWalletLoaded(wallet_path);
-}
-
 /** Return object for accessing database at specified path. */
 std::unique_ptr<WalletDatabase> CreateWalletDatabase(const fs::path& path)
 {