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.

1 files changed, 41 insertions, 0 deletions

diff --git a/library/cpp/skiff/zerocopy_output_writer.h b/library/cpp/skiff/zerocopy_output_writer.h
new file mode 100644
index 0000000000..b0bccc5a63
--- /dev/null
+++ b/library/cpp/skiff/zerocopy_output_writer.h
@@ -0,0 +1,41 @@
+#pragma once
+
+#include <util/stream/zerocopy_output.h>
+
+namespace NSkiff {
+
+////////////////////////////////////////////////////////////////////////////////
+
+// Simple wrapper around
+class TZeroCopyOutputStreamWriter
+    : private TNonCopyable
+{
+public:
+    explicit TZeroCopyOutputStreamWriter(IZeroCopyOutput* output);
+
+    ~TZeroCopyOutputStreamWriter();
+
+    Y_FORCE_INLINE char* Current() const;
+    Y_FORCE_INLINE ui64 RemainingBytes() const;
+    Y_FORCE_INLINE void Advance(size_t bytes);
+    void UndoRemaining();
+    Y_FORCE_INLINE void Write(const void* buffer, size_t length);
+    Y_FORCE_INLINE ui64 GetTotalWrittenSize() const;
+
+private:
+    void ObtainNextBlock();
+
+private:
+    IZeroCopyOutput* Output_;
+    char* Current_ = nullptr;
+    ui64 RemainingBytes_ = 0;
+    ui64 TotalWrittenBlockSize_ = 0;
+};
+
+////////////////////////////////////////////////////////////////////////////////
+
+} // namespace NSkiff
+
+#define ZEROCOPY_OUTPUT_WRITER_INL_H_
+#include "zerocopy_output_writer-inl.h"
+#undef ZEROCOPY_OUTPUT_WRITER_INL_H_