Treat "org.apache.http.legacy" as optional <uses-library> by default.

This doesn't affect the cases with explicitly set `uses_libs` or
`optional_uses_libs`, only the cases when the library implicitly added
to the manifest_fixer by Soong. "org.apache.http.legacy" should be
handled in the same way as "android.test.base", except that they have
been added in different SDK versions.

Test: lunch aosp_cf_x86_phone-userdebug && m
Bug: 132357300
Change-Id: I4fa1f082bfdb67f227f432717731a7e3d790913c