Add a <T, E> Field<Result<R>>.collecting(Collector<R, ?, E>) kotlin extension function, and similar

[lukaseder]

jOOQ 3.17 is adding <T[N], E> Field<Result<Record[N]>>.mapping(Function[N]<T[N], E>): Field<List<E>> extension methods with #12945

It would also be useful to add a few convenience shortcuts to the Collector types from Records, via:

• <T, E> Field<Result<R>>.collecting(Collector<R, ?, E>): Field<E>
• <K, V> Field<Result<Record2<K, V>>>.intoMap(): Field<Map<K, V>>
• <K, V> Field<Result<Record2<K, V>>>.intoGroups(): Field<Map<K, List<V>>>

And a few others

[lukaseder]

This is truly fantastic!! Here's the compilation test case:

@Test
fun testMultisetMapping() {
    data class C1(val i1: Int?)
    data class C2(val i1: Int?, val i2: Int?)
    data class C3(val i1: Int?, val i2: Int?, val i3: Int?)

    var s1: Select<Record1<List<C1>>> = select(multiset(select(i)).mapping(::C1))
    var s2: Select<Record1<List<C2>>> = select(multiset(select(i, j)).mapping(::C2))
    var s3: Select<Record1<List<C3>>> = select(multiset(select(i, j, k)).mapping(::C3))

    var ca1: Select<Record1<Array<Int>>> = select(multiset(select(i)).intoArray())
    var ca2: Select<Record1<Array<String>>> = select(multiset(select(i)).intoArray { it.toString() })
    var cl1: Select<Record1<List<Int>>> = select(multiset(select(i)).intoList())
    var cl2: Select<Record1<List<String>>> = select(multiset(select(i)).intoList { it.toString() })
    var cs1: Select<Record1<Set<Int>>> = select(multiset(select(i)).intoSet())
    var cs2: Select<Record1<Set<String>>> = select(multiset(select(i)).intoSet { it.toString() })
    var cm1: Select<Record1<Map<Int, Int>>> = select(multiset(select(i, j)).intoMap())
    var cm2: Select<Record1<Map<String, Record2<Int, Int>>>> = select(multiset(select(i, j)).intoMap { it.toString() })
    var cm3: Select<Record1<Map<String, String>>> = select(multiset(select(i, j)).intoMap({ it.toString() }, { it.toString() }))
    var cg1: Select<Record1<Map<Int, List<Int>>>> = select(multiset(select(i, j)).intoGroups())
    var cg2: Select<Record1<Map<String, List<Record2<Int, Int>>>>> = select(multiset(select(i, j)).intoGroups { it.toString() })
    var cg3: Select<Record1<Map<String, List<String>>>> = select(multiset(select(i, j)).intoGroups({ it.toString() }, { it.toString() }))
}

[lukaseder]

Possible alternative implementation directly in the Java API: #13539

[JayAhn2]

Nice job!