Support toLabel in SOSL queries

[adangel]

Current toLabel causes a parser error:

public with sharing class ParseErrorTest {
    public Object doSoslSearch() {

        List<List<SObject>> searchResults = [
                FIND :searchTerm
                IN ALL FIELDS
                RETURNING
                        Account(Id, toLabel(Name))
                LIMIT 10
        ];
        
        return null;        
    }
}

Error:

Syntax error at 9:43: mismatched input '(' expecting {'using', 'where', 'order', 'limit', 'offset', ')'}
Syntax error at 9:49: mismatched input ')' expecting {'instanceof', ')', '[', '.', '=', '>', '<', '?.', '?', '==', '===', '!=', '<>', '!==', '&&', '||', '??', '++', '--', '+', '-', '*', '/', '&', '|', '^', '+=', '-=', '*=', '/=', '&=', '|=', '^=', '<<=', '>>=', '>>>='}
Syntax error at 11:8: extraneous input ']' expecting ';'

sf doc: https://developer.salesforce.com/docs/atlas.en-us.soql_sosl.meta/soql_sosl/sforce_api_calls_sosl_tolabel.htm

Original reported at: pmd/pmd#5163