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, 42 insertions, 0 deletions

diff --git a/yt/cpp/mapreduce/client/client_writer.h b/yt/cpp/mapreduce/client/client_writer.h
new file mode 100644
index 0000000000..010a88a8ff
--- /dev/null
+++ b/yt/cpp/mapreduce/client/client_writer.h
@@ -0,0 +1,42 @@
+#pragma once
+
+#include <yt/cpp/mapreduce/common/fwd.h>
+
+#include <yt/cpp/mapreduce/http/requests.h>
+#include <yt/cpp/mapreduce/interface/io.h>
+
+namespace NYT {
+
+struct TTableWriterOptions;
+class TRetryfulWriter;
+
+////////////////////////////////////////////////////////////////////////////////
+
+class TClientWriter
+    : public IProxyOutput
+{
+public:
+    TClientWriter(
+        const TRichYPath& path,
+        IClientRetryPolicyPtr clientRetryPolicy,
+        ITransactionPingerPtr transactionPinger,
+        const TClientContext& context,
+        const TTransactionId& transactionId,
+        const TMaybe<TFormat>& format,
+        const TTableWriterOptions& options);
+
+    size_t GetStreamCount() const override;
+    IOutputStream* GetStream(size_t tableIndex) const override;
+    void OnRowFinished(size_t tableIndex) override;
+    void Abort() override;
+
+private:
+    ::TIntrusivePtr<TRawTableWriter> RawWriter_;
+
+    const size_t BUFFER_SIZE = 64 << 20;
+};
+
+////////////////////////////////////////////////////////////////////////////////
+
+
+} // namespace NYT