Introduce `lazyval`

[krzysiekbielicki]

WHY:

currently long boolean expressions cannot be organized and still benefit from lazy evaluation of boolean expressions

ex:

(heavyComputationFromASource1() && heavyComputationFromASource2()) || (heavyComputationFromBSource1() && heavyComputationFromBSource2()) || (heavyComputationFromCSource1() && heavyComputationFromCSource2())

is not equivalent to

val a = heavyComputationFromASource1() && heavyComputationFromASource2()
val b = heavyComputationFromBSource1() && heavyComputationFromBSource2()
val c = heavyComputationFromCSource1() && heavyComputationFromCSource2()

a || b || c

as at least *Source1() will be evaluated

PROPOSAL:

With lazyval working under the hood as some kind of supplier code below would work and still benefit from lazy evaluation

lazyval a = heavyComputationFromASource1() && heavyComputationFromASource2()
lazyval b = heavyComputationFromBSource1() && heavyComputationFromBSource2()
lazyval c = heavyComputationFromCSource1() && heavyComputationFromCSource2()

a || b || c