Fix tokenizer over-consuming character after ->> operator

[RagingKore]

Reproduction (from the issue)

var parser = new SqlQueryParser();
const string sql = """
                   select
                   category_seq as seq,
                   data.name as name,
                   meta->>'description' as description
                   from category
                   order by seq;
                   """;

var x = parser.Parse(sql, new DuckDbDialect());

Throws:

SqlParser.TokenizeException: Unterminated string literal. Expected ' after Line: 4, Col: 20
   at SqlParser.Tokenizer.TokenizeQuotedString(TokenizeQuotedStringSettings settings)
   at SqlParser.Tokenizer.TokenizeSingleQuotedString(Char quoteStyle, Boolean backslashEscape)
   ...

Root cause

TokenizeLongArrow called _state.Next() after confirming the second >, then handed off to ConsumeForBinOp which calls _state.Next() again. The character immediately following ->> was therefore silently consumed. When it was the opening ' of a string literal, subsequent tokenization walked past the closing quote and raised "Unterminated string literal".

This only surfaced when ->> was written without whitespace before the following token (e.g. meta->>'description'). Every existing test uses meta ->> 'description', where the eaten character was the harmless space — which is why it slipped through.

The fix drops the redundant _state.Next(), aligning ->> with the already-correct #>> pattern in TokenizeHash.

Tests

Added LongArrowJsonExtractionTests covering tokenization, the parser-level AST, and the exact multi-line SQL from the bug report.

The new tests are deliberately scoped to the dialects that genuinely support ->> as a JSON extraction operator: PostgreSQL, DuckDB, MySQL (since 5.7.13), SQLite (since 3.38), Redshift, and Generic. ->> is a PostgreSQL-originated extension and is not part of ANSI/ISO SQL. Dialects that use other JSON extraction mechanisms (Snowflake's col:path, BigQuery's JSON_VALUE, MS SQL's JSON_VALUE, Hive/Databricks' get_json_object, Oracle, ANSI) are intentionally excluded.

[RagingKore]

Superseded by #84 — renamed branch to bugfix/longarrow-json-extraction to match the CI workflow's branch naming convention.