156097fe17
This commit is a slightly modified revert of 4f29c113.
IS_PRE_RELEASE allows to make LATEST_STABLE version behave as
experimental when this flag is set to true.
The general goal is to prepare fix of KT-62058; after this commit
one can do it by changing IS_PRE_RELEASE flag to true.
The fix of KT-62058 is planned to be done during bootstrapping.
This preparation and the future fix are parts of umbrella KT-61951.