Move configuration checks from getBootImageJar

The getBootImageJar function will be removed once the boot image
creation has been moved to the platform_bootclasspath and
bootclasspath_fragment module types. However, the consistency checks
that it performs are still useful so this change moves them out
first.

The ART boot image related checks are now performed in the
bootclasspath_fragment module type. A previous change accidentally
disabled the checks when the contents property was not empty which has
been fixed. Also, the error messages have been tweaked to make it clear
that the art-bootclasspath-fragment is now the source of truth as to
its contents not the configuration.

The framework boot image related checks are now performed in the
platform_bootclasspath module type.

Initially, this change included an extra check to make sure that
UpdatableBootJars comes from updatable APEXes but that broke because
framework-wifi and framework-tethering are not currently marked as
updatable in AOSP.

Bug: 177892522
Test: m nothing
Change-Id: I80fb600fa2c7cec4566b3461c6a33c4c6f0743f4