The `ConcurrentCollectionFactory` class was moved to the module
which is no longer available in the 213 platform distribution
`MapMaker().weakKeys().makeMap()` is used as drop-in replacement of
concurrent hash map with identity-based equals strategy
The new implementation stores keys on weak references, which should not
change the behavior of the `ModuleFileCacheImpl`.
1. If someone still has a strong reference to the `ktFile`, then the
cache will also keep it.
2. If there are no more strong references to the `ktFile`, then the
cache will not hold it from being garbage-collected. However, since
nobody has a strong reference to the `ktFile` anymore, nobody can call
`fileCached` or `getCachedFirFile` with it, and it will never be
requested from the cache.
KTI-1114
Roman Golyshev
fb9de6ba45