Move ro.boot.dynamic_partitions to vendor/build.prop

Bug: 132197773
Test: property present in vendor/build.prop

Currently, the property resides in product partition which gets
overwritten by the GSI image. Moving it to vendor will ensure
that the property is set even when a GSI image is flashed on the device.

Change-Id: I4d4a3c473194e15ba124a121f89bbb3ec1a73d19