YQL-19616 Convert YQL lexer grammar to regexes

- [x] Parse YQL grammar to extract lexer grammar into `TLexerGrammar`.
- [x] Translate `TLexerGrammar` into regexes.
- [x] Implement a lexer via regexes `TRegexLexer` to test generated regexes validity.
- [x] Test on `Default` syntax mode.
- [x] Test on `ANSI` syntax mode.

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- Related to https://github.com/ydb-platform/ydb/issues/15129
- Requirement for https://github.com/ytsaurus/ytsaurus/pull/1112

---

Pull Request resolved: https://github.com/ytsaurus/ytsaurus/pull/1127
commit_hash:03ffffe81cdafe7f93a4d3fd9a3212fe67f1c72d

1 files changed, 18 insertions, 0 deletions

diff --git a/yql/essentials/sql/v1/reflect/sql_reflect.h b/yql/essentials/sql/v1/reflect/sql_reflect.h
new file mode 100644
index 00000000000..5225a3c996b
--- /dev/null
+++ b/yql/essentials/sql/v1/reflect/sql_reflect.h
@@ -0,0 +1,18 @@
+#pragma once
+
+#include <util/generic/string.h>
+#include <util/generic/hash_set.h>
+#include <util/generic/hash.h>
+
+namespace NSQLReflect {
+
+    struct TLexerGrammar {
+        THashSet<TString> KeywordNames;
+        THashSet<TString> PunctuationNames;
+        THashSet<TString> OtherNames;
+        THashMap<TString, TString> BlockByName;
+    };
+
+    TLexerGrammar LoadLexerGrammar();
+
+} // namespace NSQLReflect