prebuilts: Oniro toolchain and 3rd party prebuilts for OpenHarmony

This provides recipe oniro-openharmony-toolchain and oniro-openharmony-bundle
recipes, which will build SDK images (self-extractable .sh file), which can be
installed into an OpenHarmony source repository, and provides alternative
toolchain and 3rd party components from Oniro project to the ones provided by
OpenHarmony project.

The oniro-openharmony-toolchain image provides prebuilt clang and musl libc
toolchain, and oniro-openharmony-bundle image extends that with various
prebuilt third-party components.

Signed-off-by: Esben Haabendal <esben.haabendal@huawei.com>