Use java_import to rename jars

- Apparently, the old way of renaming the jar file broke the renaming
effect in conjunction with ag/33582071.

Use java_import to make sure they get renamed.

- Also add empty jars to ravenwood-runtime to override potential
left over jar files from the previous attempt of ag/33582071.

- Also add the cleanspec, in case it works.

Bug: 292141694
Flag: TEST_ONLY
Test: ./ravenwood/scripts/run-ravenwood-tests.sh -r
Test: manually verify the content of ravenwood-runtime:

$ ls -l $ANDROID_BUILD_TOP/out/host/linux-x86/testcases/ravenwood-runtime/ | sort -k 9
-rw-r--r-- 1 omakoto primarygroup 33340707 May 16 12:31 100-framework-minus-apex.ravenwood.jar
-rw-r--r-- 1 omakoto primarygroup    43875 May 16 12:31 200-kxml2-android.jar
    :
-rw-r--r-- 1 omakoto primarygroup       22 May 16 12:31 framework-minus-apex.ravenwood.jar
-rw-r--r-- 1 omakoto primarygroup       22 May 16 12:47 kxml2-android.jar

Change-Id: Id1f3f3166c6c004249690964d5a0a78e0897d5c1