RFC: A resettable Lazy alternative

[SomeTroglodyte]

An experiment: What if there were a way to tell a by lazy { ... } field that its cached value is obsolete?

This is just the tool and its unit tests... But if liked, we could refactor some existing fields - see resetAdjacentToRiverTransient? Should be oodles of candidates, but that was the only direct example I could find.

Notes:

• Can't reflect-hack the existing Lazy as it forgets its initializer lambda as soon as it is tripped
• Not 100% compatible as inheriting from Lazy directly breaks it - the compiler no longer does as it is told, the Lazy thing must have hardcoded support one cannot modify - we inherit and we're no longer actually instantiated even if the constructor call is explicit. The field gets a SafePublicationLazyImpl delegate instead.
• Won't get the Lazy optimization that a tripped lazy will get its delegate replaced by the much faster InitializedLazyImpl stub - one, need to keep knowledge about initializer, two, that seems to be done compiler-hardcoded too: There's a writeReplace method but I don't see where it is called, actually it can't really be legally called as it is private...

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