fixed EA-55872 - NPE: PyProtectedMemberInspection$Visitor.checkReference
apply laf once, fix stale bg, add beforeShown() & preselect laf-default editor scheme
fixed EA-55749 - AIOOBE: PyStructuredDocstringFormatter.formatDocstring
fixed EA-54835 - NPE: PythonNoseTestConfigurationProducer.isAvailable
[vcs] Reuse the VirtualFile instead of creating FilePathImpl on File

Relates to IDEA-119996
IDEA-119996 FilePathImpl: avoid VFS refresh from getVirtualFile etc.

Actually, a revert of e31663b & ee19cc4 & 57c4367.

There is the public refresh() methods for those who needs to refresh.
Otherwise getPath(), isDirectory() and getVirtualFile() itself are
accessed from too many places and too often, and clients are not
aware that it may be costly to call this method frequently.
Merge remote-tracking branch 'origin/master'