Add non-symbolic base version of network-wireless-bluetooth icons

Currently these icons only exist with the -symbolic suffix, meaning if anything tries to access them without the suffix in the request, they won't find it and will get back network-wireless instead, which looks different and would constitute a visual bug.

Rename these icons to be named network-wireless-bluetooth and then add symlinks for the -symbolic versions.

@iasensio do you remember this history here?