apf: Increase test coverage of LDDW / STDW

Add testcases covering interesting combinations of offset size and sign.
Also adjust a few existing testcases to increase interpreter coverage.

Bug: 73804303
Test: runtest -x tests/net/java/android/net/apf/ApfTest.java
Change-Id: I7f1a9166e81656711c57af7c72608e53666aae6f