fix: revert all unrelated upstream develop changes from phase-7 PR

Reverts 259 files that carried unrelated upstream changes through the
phase-6 merge: enum class removals (cppcoreguidelines-use-enum-class),
scoped_lock→lock_guard conversions (modernize-use-scoped-lock),
nodestore Backend API changes (void const* key), .clang-tidy config,
test infrastructure deletions, and miscellaneous develop changes.

These changes belong on develop, not in the telemetry PR chain.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

src/libxrpl/basics/ResolverAsio.cpp

@@ -177,7 +177,7 @@ public:
         if (m_stopped.exchange(false))
         {
             {
-                std::lock_guard const lk{m_mut};
+                std::scoped_lock const lk{m_mut};
                 m_asyncHandlersCompleted = false;
             }
             addReference();