[Variant] Support escaping mechanism for `VariantPath` parsing

[alamb]

My immediate question from this is "is there an escape mechanism to allow for "." in a field name?". I checked and the answer's no. That's fine but it might be worth a note.

Originally posted by @mhilton in #8945 (comment)

According to DataBricks the path https://docs.databricks.com/gcp/en/sql/language-manual/functions/variant_get

. path: A STRING literal with a well-formed JSON path expression.

The internet suggests that JSON path escaping looks like they follow the JSON escaping rules

(aka " should be \")

https://ietf-wg-jsonpath.github.io/draft-ietf-jsonpath-base/draft-ietf-jsonpath-base.html#name-name-selector

https://www.rfc-editor.org/rfc/rfc8259#section-7

[mhilton]

Databricks's JSON path expression is documented here, and doesn't appear to be the same as rfc8592 JSON path. Although they are similar. Full support of the JSONPath RFC doesn't really make sense in this context so I suggest implementing Databrick's flavour.

Looking through the docs it does have some interesting properties. For example in the .<field>. notation (as opposed to the .["field"]. notation) the field is treated as case-insensitive but only matches if there is a single case-insensitive match.