Add CollationRoot to preloaded classes

It was determined this would save RAM.

Test: ./generate-preloaded-classes.sh base.txt preloaded-classes-blacklist preloaded-classes-extra  > preloaded-classes
Test: Look at the generated file
Bug: 63444758
Change-Id: Ib49b1218e94e4a4a2211071da189cf917559248b
diff --git a/config/preloaded-classes-extra b/config/preloaded-classes-extra
new file mode 100644
index 0000000..1934cbc
--- /dev/null
+++ b/config/preloaded-classes-extra
@@ -0,0 +1 @@
+android.icu.impl.coll.CollationRoot