Python-jsonpath

**IETF JSONPath Draft compliance**

- **Behavioral change.** When applied to a JSON object, filters now have an implicit preceding wildcard selector and the "current" (``) object is set to each of the object's values. This is now consistent with applying filters to arrays and adheres to the IETF JSONPath Internet Draft.

**IETF JSONPath Draft compliance**

- Added support for function extensions.
- Added the built-in `length()` function.
- Added the built-in `count()` function. `count()` is an alias for `length()`.
- Support filters without parentheses.
- Adhere to IETF JSONPath draft escaping in quoted property selectors.
- Handle UTF-16 surrogate pairs in quoted property selectors.

**Features**

- Added the built-in `keys()` function.
- Added `parent` and `children` properties to `JSONPathMatch`. Now we can traverse the "document tree" after finding matches.
- Added a `parts` property to `JSONPathMatch`. `parts` is a tuple of `int`s, `slice`s and `str`s that can be used with `JSONPathEnvironment.getitem()` to get the matched object from the original data structure, or equivalent data structures. It is the keys, indices and slices that make up a concrete path.

**Fixes**

- Fixed a bug with `CompoundJSONPath.finditer()` and the intersection operator (`&`). The intersection operation was returning just the left hand results.

**Fixes**

- Fixed normalized paths produced by `JSONPathNode.path()`. Previously we were not handling some escape sequences correctly in name selectors.
- Fixed serialization of `JSONPathQuery` instances. `JSONPathQuery.__str__()` now serialized name selectors and string literals to the canonical format, similar to normalized paths. We're also now minimizing the use of parentheses when serializing logical expressions.
- Fixed parsing of filter queries with multiple bracketed segments.

**Fixes**

- Fixed decoding of escape sequences in quoted name selectors and string literals. We now raise a `JSONPathSyntaxError` for invalid code points.
- Fixed parsing of number literals with an exponent. We now allow 'e' to be upper case.
- Fixed handling of trailing commas in bracketed segments. We now raise a `JSONPathSyntaxError` in such cases.
- Fixed handling of invalid number literals. We now raise a syntax error for invalid leading zeros and extra negative signs.

**Fixes**

- Handle end of query when lexing inside a filter expression.
- Check patterns passed to `search` and `match` are valid I-Regexp patterns. Both of these functions now return _LogicalFalse_ if the pattern is not valid according to RFC 9485.