[native_toolchain_c] Tool groups

Currently, our tool resolution abstraction does not really have a solution for resolving groups of tools.

Take for example https://github.com/dart-lang/native/blob/main/pkgs/native_toolchain_c/lib/src/native_toolchain/clang.dart, it has a `clang`, `ar`, and `ld`. If multiple clang installations are available on the system, but one is missing one of these 3 tools (for some obscure reason), we would only want to return tools from the complete clang installation.