write "singleton=<value>" if it was specified explicitly
IDEA-80056 Column selection mode improvement

CaretModel API changes - passing Caret instance to runForEachCaret callback, and some minor ones
avoid problem with concurrent clearing of timestamp cache between thread saving indexed attributes (e.g. indexer thread) and another one (e.g. flushing thread)
- indexing by unindexedfilefinder (root dependent cache updater) removes indexed file from filesToUpdate set
- when removing outdated data reset file indexed attribute for later being able to index unindexedfilefinder (root dependent cache updater)
removed debug field