Cover absolute path filter queries

[Marcono1234]

It might be good to add tests for using an absolute path (that is $ instead of @) in a filter selector, e.g. $[?$.a==1]. Currently the filter tests only seem to cover relative paths (@) or invalid selectors with absolute paths, but not any valid selectors with absolute paths.

Might be good to cover:

• existence test without segment: $[?$]
• some 'normal' filter expressions, e.g. $[?$.a==1]
• using (...), e.g. $[?($.a==1)]
• equals self: $[?$==$] (similar to #71)
• equals with relative path
  • selector: $[?@[0] == $[0]] and $[?$[0] == @[0]]
  • document: [0, [0, 1], [1, 2]]
• applying the filter selector to a nested value and making sure $ is evaluated absolute and not relative, for example:
  • selector: $.a[?$.b==2]
  • document: {"a": [{"b": 1}], "b": 2}

What do you think?

[gregsdennis]

https://github.com/jsonpath-standard/jsonpath-compliance-test-suite/blob/7bd8532dfcccd288bbcaa67b48e5804911991094/tests/filter.json#L573-L647

What we need is absolute singular query tests.