Add flags to bendini to decide what to do about version conflicts

[sakarias88]

An example we have today when we deploy "new" functions where we first register and upload attachments before checking if we can actually register the function. This means we upload orphaned attachments just because function registry fails.

We must always check if the function exists but we need a flag to decide what to do in case it finds an already registered function.

Right now a duplicate counts as a function with same name and version. The code might still be different though. This flag is for deciding the strictness of the check. It could for example compare the checksums between the local version and the already uploaded version. Skip all duplicates, skip duplicates with matching checksum, skip no duplicates. --skip-duplicates all/matching-manifest/matching-checksum/none