Python: Get rid of points-to from Definitions.qll

Turns out the `ImportTime` module (despite living in
`semmle.python.types` does not actually depend on points-to, so some of
the `LegacyPointsTo` imports could be replaced or removed.

python/ql/src/Imports/Cyclic.qll

@@ -1,5 +1,6 @@
 import python
 private import LegacyPointsTo
+private import semmle.python.types.ImportTime
 
 predicate is_import_time(Stmt s) { not s.getScope+() instanceof Function }
 

python/ql/src/Imports/UnintentionalImport.ql

@@ -14,6 +14,7 @@
 
 import python
 private import LegacyPointsTo
+private import semmle.python.types.ImportTime
 
 predicate import_star(ImportStar imp, ModuleValue exporter) {
   exporter.importedAs(imp.getImportedModuleName())

python/ql/src/Variables/UndefinedGlobal.ql

@@ -12,6 +12,7 @@
 
 import python
 private import LegacyPointsTo
+private import semmle.python.types.ImportTime
 import Variables.MonkeyPatched
 import Loop
 

python/ql/src/Variables/UndefinedPlaceHolder.ql

@@ -14,6 +14,7 @@
 import python
 import Variables.MonkeyPatched
 private import LegacyPointsTo
+private import semmle.python.types.ImportTime
 
 /* Local variable part */
 predicate initialized_as_local(PlaceHolder use) {