ClickHouse: Add fuzz target comparing the tokenizer with ClickHouse's lexer #2645

The lexer is vendored from https://github.com/ClickHouse/clickhouse-lexer
(ClickHouse src/Parsers/Lexer.cpp at the commit recorded in COMMIT,
Apache 2.0) and compiled natively with LEXER_STANDALONE_BUILD, the same
configuration ClickHouse uses for its WebAssembly build. It builds behind the
clickhouse feature like the other oracle targets, so ClusterFuzzLite picks it
up without workflow changes.