PY-12018 Optimize imports detects that imports are reordered

It also doesn't leave stale IMPORT_GROUP_BEGIN flags in user data
that confuses formatter afterwards.

python/testData/refactoring/move/module/after/src/a.py

@@ -1,7 +1,7 @@
 from p1 import m1
+import p1
 from p1.m1 import foo
 import p1.m1
-import p1
 
 p1.m1.foo
 m1.bar

python/testData/refactoring/move/relativeImportsToModulesInSameMovedPackageNotUpdated/after/src/subpkg/m1.py

@@ -1,8 +1,8 @@
-from . import m2
 import m3
-import subsubpkg as foo
-from . import subsubpkg as bar
-from .subsubpkg import m4
 from pkg import m5
+import subsubpkg as foo
+from .subsubpkg import m4
+from . import m2
+from . import subsubpkg as bar
 
 print(m2, m3, m4, m5, foo, bar)