Merge #20275: wallet: List all wallets in non-SQLite and non-BDB builds

f3d870fc22 wallet: List all wallets in non-SQLite or non-BDB builds (Russell Yanofsky)
d70dc89e78 refactor: Consolidate redundant wallet database path and exists functions (Russell Yanofsky)
6a7a63644c refactor: Drop call to GetWalletEnv in wallet salvage code (Russell Yanofsky)
6ee9cbdd18 refactor: Replace ListWalletDir() function with ListDatabases() (Russell Yanofsky)
5aaeb6cf87 MOVEONLY: Move IsBDBFile, IsSQLiteFile, and ListWalletDir (Russell Yanofsky)

Pull request description:

  This PR does not change behavior when bitcoin is built normally with both the SQLite and BDB libraries. It just makes non-SQLite and non-BDB builds more similar to the normal build. Specifically:

  - It makes wallet directory lists always include all wallets so wallets don't appear missing depending on the build.

  - It now triggers specific "Build does not support SQLite database format" and "Build does not support Berkeley DB database format" errors if a wallet can't be loaded instead of the more ambiguous and scary "Data is not in recognized format" error.

  Both changes are implemented in the last commit. The previous commits are just refactoring cleanups that make the last commit possible and consolidate and reduce code.

ACKs for top commit:
  achow101:
    ACK f3d870fc22
  promag:
    Tested ACK f3d870fc22. Tested a --without-sqlite build with sqlite wallets.

Tree-SHA512: 029ad21559dbc338b5f351d05113c51bc25bce830f4f4e18bcd82287bc528275347a60249da65b91d252632aeb70b25d057bd59c704bfcaafb9f790bc5b59762

src/wallet/interfaces.cpp

@@ -551,7 +551,7 @@ public:
     std::vector<std::string> listWalletDir() override
     {
         std::vector<std::string> paths;
-        for (auto& path : ListWalletDir()) {
+        for (auto& path : ListDatabases(GetWalletDir())) {
             paths.push_back(path.string());
         }
         return paths;