Add support for iterating records

[pubudu91]

Purpose

This PR adds support for iterating through the fields of a record. Fix #10080

Goals

• Support for using records with foreach
• Support for iterable operations for records

Samples

Foreach loop

Person p = { name: "John Doe", age: 25, address: { street: "Palm Grove", city: "Colombo 3" } };

foreach f, v in p {
    io:println(f + ":" + <string>v);
}

Iterable operations

Foo f = {a: "AA", b: "BB", c: "CC", d: "DD", e: "EE"};

Foo newf = f.map(((string, any) entry) => (string, any) {
                var (field, value) = entry;
                match value {
                    string str => value = str.toLower();
                    any => {}
                }
                return (field, value);
            })
            .filter(((string, any) entry) => boolean {
                var (field, value) = entry;
                if (value != "aa" && value != "ee") {
                    return true;
                }
                return false;
            });

Test environment

Ubuntu Gnome 16.04 LTS, JDK 1.8

[pubudu91]

Closing this since I'm working on fixing a bug related to this which I came across when addressing the comments/suggestions raised during the review.