Expose errors in query parser

[rnewman]

We currently completely collapse errors from combine in mentat_query_parser:

#[derive(Clone, Debug, Eq, PartialEq)]
pub enum WhereParseError {
    Err,
}

…

pub fn clause_seq_to_patterns(clauses: &[edn::Value]) -> WhereParseResult {
    Where::clauses()
        .parse(clauses)
        .map(|x| x.0)
        .map_err(|_| WhereParseError::Err)
}

After Marwes/combine#87, we'll be better able to turn these errors into something that's meaningful to propagate out of the query interface.