Separate the computation of all config IDs

We will need this in another place, so we abstract the 'compute all
current IDs' functionality into a separate function. We also change the
name of the _ComputeAllLVs to _AllLVs to match the other _All*s
functions.

Signed-off-by: Iustin Pop <iustin@google.com>
Reviewed-by: Michael Hanselmann <hansmi@google.com>