[FR] Support disabling top-level library linking

Currently, when the NDK rules are used in conjunction with the regular Android rules (rules_android), the default behavior is to link all cc_library deps into one single .so file that gets packaged into the APK. Some users have requested the ability to disable the top-level linking, i.e. to have disparate .so files corresponding to each cc_library.

To support this, we'd need something like [this](https://github.com/bazelbuild/rules_android/blob/main/rules/native_deps.bzl#L366-L374) in the NDK rules themselves.