PRODUCT_MANIFEST_PACKAGE_NAME_OVERRIDES is applicable to override_apex

apex { name: "foo" }
override_apex { name: "override_foo", base:"foo" }

PRODUCT_MANIFEST_PACKAGE_NAME_OVERRIDES := foo:com.android.foo

Previously, the override was done only for the overridden package "foo",
but not for "override_foo". Fixing this issue by using ctx.ModuleName()
when finding the package name to use.

Exempt-From-Owner-Approval: cherry-pick from internal

Bug: 150645663
Test: m
Merged-In: I2947e5c75369216a4bbce8749503236be86771c3
(cherry picked from commit a519c54d)
Change-Id: I2947e5c75369216a4bbce8749503236be86771c3