fix(types): parse JSON type hints with parenthesized types

[hsdfat]

Summary

Fixes #442.

JSON columns with a typed path whose type has its own parentheses could not be parsed from the RowBinaryWithNamesAndTypes header, so reading from or inserting into such a table failed:

CREATE TABLE t (bar JSON(test Nullable(String))) ENGINE = MergeTree
-> type parsing error: Unknown data type: Strin

Two independent problems in parse_json():

• remove_json_header() used trim_end_matches(')'), stripping every trailing ) instead of just the one closing JSON(, so JSON(a Nullable(String)) became a Nullable(String and the inner type parsed as Strin.
• The hint list was split on commas and settings were detected by = without tracking parentheses or string literals (only back-quoted paths were handled, since fix(types): parse back-quoted JSON path names #458). So JSON(a Map(String, Int32)) was split into two broken hints, JSON(a Enum8('x' = 1)) silently lost its hint because it looked like a name=value setting, and a SKIP REGEXP pattern containing a comma was split as well.

The fix

remove_json_header() now strips exactly JSON( and one closing ). The splitting helper introduced in #458 now also skips separators inside parentheses and single-quoted literals (renamed from unquoted_positions to top_level_positions), and is still used for the hint separator, the setting = check and the path/type boundary. Settings (max_dynamic_paths=N), SKIP, SKIP REGEXP and back-quoted paths behave as before; the existing tests are unchanged.

Verification

New unit test test_data_type_new_json_with_nested_hint_types, on main:

$ cargo test -p clickhouse-types --lib test_data_type_new_json
test data_types::tests::test_data_type_new_json_with_nested_hint_types ... FAILED
called `Result::unwrap()` on an `Err` value: TypeParsingError("Unknown data type: Strin")

With the fix, cargo test -p clickhouse-types passes (44 + 1 doctest). cargo fmt -- --check and cargo clippy -p clickhouse-types --all-targets are clean with RUSTFLAGS=-Dwarnings.

Checklist

• Unit tests covering the common scenarios were added
• A human-readable description of the changes was provided so that we can include it in CHANGELOG later

Suggested CHANGELOG entry (Fixed): JSON columns with typed paths whose type has parentheses, e.g. JSON(a Nullable(String)) or JSON(a Map(String, Int32)), no longer fail to parse. ([#442])

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