Add desugar_java8_libs tests

[Bencodes]

Test that repros the following issue: #457

Run the following test cases to repro:

# Expected to fail
bazel test //test/rules/android_binary/r8_integration:r8_desugaring_test

# Expected to pass, currently does not.
bazel test //test/rules/android_binary/r8_integration:r8_desugaring_test --desugar_java8_libs

[ted-xie]

We're going to absorb this into #471.