java completion: enable package suggestions inside type arguments (IDEA-193049)

java/java-tests/testData/codeInsight/completion/normal/PackageInMemberTypeGeneric.java

@@ -0,0 +1,3 @@
+class Foo {
+  List<java.la<caret>> foo() {}
+}

java/java-tests/testData/codeInsight/completion/normal/PackageInMemberTypeGeneric_after.java

@@ -0,0 +1,3 @@
+class Foo {
+  List<java.lang.<caret>> foo() {}
+}