Disable installation of ART modules in /system.

Remove ART modules (`art-runtime`, `art-tools`) from `PRODUCT_PACKAGES`, as
they are provided by the Android Runtime APEX module
(`com.android.runtime`).

Copy of rpl's http://r.android.com/812674.

Test: Flash and boot
Test: atest CtsJniTestCases
Test: atest CtsJdwpTestCases
Test: m checkbuild dist
Bug: 113373927
Change-Id: I3e0c130f1a9c596629ab243648f0251cf71c1499