jsonpath: add jsonpath conditional evaluation

jsonpath: add jsonpath conditional evaluation

This commit adds support for evaluating jsonpath conditionals.
Conditionals have the structure of $ ? (predicate), and will filter
the current json objects based on whether they satisfy the predicate
expression. Additionally, this commit introduces @, which represents
the current json object so filters can be used to reference the object
being evaluated.

Informs: #142610
Epic: None
Release note (sql change): Add jsonpath filters, which take on the form
$ ? (predicate), allowing results to be filtered.

jsonpath/eval: add unwrap parameter to jsonpath.eval

Previously, jsonpath conditionals/filters would unwrap infinitely. For
example, SELECT jsonb_path_query('{"a": [[[[{"b": 1}]]]]}', '$.a ? (@.b == 1)');
would return an entry, when postgres would not. This commit adds an
unwrap boolean parameter to eval, which allows for control over when
to stop unwrapping json arrays. Additionally, this commit updates
eval to take in a json.JSON rather than a []json.JSON, simplifying
the evaluation logic.

Epic: None
Release note: None