@NotNull
diff: rename 'Cancel' to 'Revert' button in merge

This action will undo all changes, that was made during merge, so 'cancel' could be not clear enough
diff: add dummy progress before dialog in 'external tool' dialog
diff: extract method
IDEA-101657 diff: call "doCancelAction()" instead of "close()" on EditSource with active modal diff dialog

this allows to handle such dialog cancellation in corresponding dialog
SettingsTreeView: fix sorting after search