YT-19324: move YT provider to ydb/library/yql

This commit is formed by the following script: https://paste.yandex-team.ru/6f92e4b8-efc5-4d34-948b-15ee2accd7e7/text.
This commit has zero effect on all projects that depend on YQL.

The summary of changes:
- `yql/providers/yt -> ydb/library/yql/providers/yt `- the whole implementation of YT provider is moved into YDB code base for further export as a part of YT YQL plugin shared library;
- `yql/providers/stat/{expr_nodes,uploader} -> ydb/library/yql/providers/stat/{expr_nodes,uploader}` - a small interface without implementation and the description of stat expr nodes;
- `yql/core/extract_predicate/ut -> ydb/library/yql/core/extract_predicate/ut`;
- `yql/core/{ut,ut_common} -> ydb/library/yql/core/{ut,ut_common}`;
- `yql/core` is gone;
- `yql/library/url_preprocessing -> ydb/library/yql/core/url_preprocessing`.

**NB**: all new targets inside `ydb/` are under `IF (NOT CMAKE_EXPORT)` clause which disables them from open-source cmake generation and ya make build. They will be enabled in the subsequent commits.

2 files changed, 65 insertions, 0 deletions

diff --git a/library/cpp/yt/memory/leaky_ref_counted_singleton-inl.h b/library/cpp/yt/memory/leaky_ref_counted_singleton-inl.h
new file mode 100644
index 00000000000..1fba63c427a
--- /dev/null
+++ b/library/cpp/yt/memory/leaky_ref_counted_singleton-inl.h
@@ -0,0 +1,43 @@
+#ifndef LEAKY_REF_COUNTED_SINGLETON_INL_H_
+#error "Direct inclusion of this file is not allowed, include leaky_ref_counted_singleton.h"
+// For the sake of sane code completion.
+#include "leaky_ref_counted_singleton.h"
+#endif
+
+#include "new.h"
+
+#include <atomic>
+#include <mutex>
+
+#include <util/system/compiler.h>
+#include <util/system/sanitizers.h>
+
+namespace NYT {
+
+////////////////////////////////////////////////////////////////////////////////
+
+template <class T, class... TArgs>
+TIntrusivePtr<T> LeakyRefCountedSingleton(TArgs&&... args)
+{
+    static std::atomic<T*> Ptr;
+    auto* ptr = Ptr.load(std::memory_order::acquire);
+    if (Y_LIKELY(ptr)) {
+        return ptr;
+    }
+
+    static std::once_flag Initialized;
+    std::call_once(Initialized, [&] {
+        auto ptr = New<T>(std::forward<TArgs>(args)...);
+        Ref(ptr.Get());
+        Ptr.store(ptr.Get());
+#if defined(_asan_enabled_)
+        NSan::MarkAsIntentionallyLeaked(ptr.Get());
+#endif
+    });
+
+    return Ptr.load();
+}
+
+////////////////////////////////////////////////////////////////////////////////
+
+} // namespace NYT
diff --git a/library/cpp/yt/memory/leaky_ref_counted_singleton.h b/library/cpp/yt/memory/leaky_ref_counted_singleton.h
new file mode 100644
index 00000000000..d77c3c98294
--- /dev/null
+++ b/library/cpp/yt/memory/leaky_ref_counted_singleton.h
@@ -0,0 +1,22 @@
+#pragma once
+
+#include "intrusive_ptr.h"
+
+namespace NYT {
+
+////////////////////////////////////////////////////////////////////////////////
+
+#define DECLARE_LEAKY_REF_COUNTED_SINGLETON_FRIEND()    \
+    template <class T>                                  \
+    friend struct ::NYT::TRefCountedWrapper;
+
+template <class T, class... TArgs>
+TIntrusivePtr<T> LeakyRefCountedSingleton(TArgs&&... args);
+
+////////////////////////////////////////////////////////////////////////////////
+
+} // namespace NYT
+
+#define LEAKY_REF_COUNTED_SINGLETON_INL_H_
+#include "leaky_ref_counted_singleton-inl.h"
+#undef LEAKY_REF_COUNTED_SINGLETON_INL_H_