Remove WalletDatabase::Create, CreateMock, and CreateDummy

Summary:
These are superseded by CreateWalletDatabase, CreateMockWalletDatabase,
and CreateDummyWalletDatabase

This concludes backport of [[bitcoin/bitcoin#19310 | core#19310]] [3/3]
bitcoin/bitcoin@da7a83c

Test Plan: `ninja all check-all`

Reviewers: #bitcoin_abc, deadalnix

Reviewed By: #bitcoin_abc, deadalnix

Differential Revision: https://reviews.bitcoinabc.org/D9621

src/wallet/bdb.h

@@ -121,29 +121,6 @@ class BerkeleyDatabase {
         }
     }
 
-    /** Return object for accessing database at specified path. */
-    static std::unique_ptr<BerkeleyDatabase> Create(const fs::path &path) {
-        std::string filename;
-        return std::make_unique<BerkeleyDatabase>(GetWalletEnv(path, filename),
-                                                  std::move(filename));
-    }
-
-    /**
-     * Return object for accessing dummy database with no read/write
-     * capabilities.
-     */
-    static std::unique_ptr<BerkeleyDatabase> CreateDummy() {
-        return std::make_unique<BerkeleyDatabase>();
-    }
-
-    /**
-     * Return object for accessing temporary in-memory database.
-     */
-    static std::unique_ptr<BerkeleyDatabase> CreateMock() {
-        return std::make_unique<BerkeleyDatabase>(
-            std::make_shared<BerkeleyEnvironment>(), "");
-    }
-
     /**
      * Rewrite the entire database on disk, with the exception of key pszSkip if
      * non-zero