Added slashes in generated tests when they are invoked on directory.

This makes it easier to find directory for test using IDEA's go to file/search everywhere features.
Analyzing 'when' expression refactoring
collect data flow infos for branch with many conditions
Refactoring: extracted 'getDataFlowInfosForEntryCondition'
Removed duplicated code
KT-5182 Data flow info is lost for 'when' branches
  #KT-5158 Fixed
  #KT-4332 Fixed
Refactoring: extracted 'reportUnreachableCode'
Rename: getAllInstructions -> getInstructionsIncludingDeadCode
Added this method to 'Pseudocode' interface instead of 'getDeadInstructions',
added 'isDead' to 'Instruction' interface
Added NotNull annotation
Highlight all text ranges for diagnostics in tests
Added 'PARTLY_UNREACHABLE_CODE' error
Mark only unreachable parts of element if it has reachable parts
 like for 'return todo()' mark only 'return'