Move ExtServices in com.android.ext apex.

Bug: 147674123
Test: built on aosp_taimen and verified package is available from the
apex.

Change-Id: I59c070cf9b4ea6afef590888849de96ead84fde2
diff --git a/target/product/base_system.mk b/target/product/base_system.mk
index 11d448a..2854df8 100644
--- a/target/product/base_system.mk
+++ b/target/product/base_system.mk
@@ -54,6 +54,7 @@
     com.android.appsearch \
     com.android.conscrypt \
     com.android.cronet \
+    com.android.extservices \
     com.android.i18n \
     com.android.ipsec \
     com.android.location.provider \
@@ -83,7 +84,6 @@
     dumpsys \
     DynamicSystemInstallationService \
     e2fsck \
-    ExtServices \
     ExtShared \
     flags_health_check \
     framework-minus-apex \