singleton instances for internal file types
move check for isProjectOrWorkspaceFile to be after project's isInContent condition, to avoid content loading for non project files via getFileType() content detection  (IDEA-133507)
more optimal isProjectOrWorkspaceFile calculation
use ProjectCoreUtil.isProjectOrWorkspaceFile
more optimal isProjectOrWorkspaceFile calculation
twice smaller data for indexing stamp
- do not file.getFileType() to avoid autodetection by content loading for arbitrary files
- use ProjectCoreUtil when possible
EA-63198 - IAE: XDebuggerManager.getInstance
if compiled class is associated with multiple sources, correctly update class data for not compiled associated sources
extract method: resolve conflicts during params rename (IDEABKL-3749)
extract method: @Nullable
extract method: new signature detector (IDEA-66281); initial
[log] Don't store VcsUser duplicates: intern them.