Support using java_sdk_library components in stub_libs

Previously, if a bootclasspath_fragment had both a java_sdk_library
module and one of its components in stub_libs properties they would be
treated as separate modules instead of simply different APIs from the
same module. That would result in them both providing stub dex jars to
"hiddenapi list" which would fail because it found duplicate
definitions of the same class.

e.g. Specifying something like this:
    api: {
        stub_libs: [
            "art.module.public.api",
        ],
    },
    core_platform_api: {
        stub_libs: [
            "art.module.public.api.stubs.module_lib",
        ],
    },

would cause "hiddenapi list" to fail because it would have been passed
paths to two dex jars (actually the same dex jar but that does not
matter) each of which defined the same class, e.g. java.lang.Object.

This change treats the "art.module.public.api.stubs.module_lib" and
"art.module.public.api" modules as being the same for the purposes of
hidden API processing.

Bug: 192446466
Test: m nothing
Change-Id: I9de96337f64f26e24cff040d4bbed9eecc67b1ed