Are tags longer than 128 bit possible for AES-256-CCM and AES-256-GCM?
No, there is no black-box type way of increasing the security strength of the tags of CCM and GCM. Because in this case you would apply a deterministic function which couldn't bring you any increases in security as a collision on the input would still lead to a collision on the output.

For CCM there is also no non-black box type of way, at least if you want to stick to AES. This is because CCM uses CMAC internally which is close to CBC-MAC which is CBC adapted for authentication. The authentication tag for CMAC is the result of an AES encryption and AES is solely specified for 128-bit blocks (which is the size of the AES in- and output).

GCM is similar in that respect to CCM, in that the output of the polynomial hash function is actually XOR encrypted with the output of an AES block. However if you pick a longer polynomial for GCM (which will instantly break all implementations you may have) and if you maybe make some educated changes to how often the polynomial gets evaluated, you might get a stronger tag as the result. However this would most-likely be a GCM look-a-like, but would needs its own (difficult) security analysis and new implementations.

On a final note, the tags of CCM,  GCM and HMAC are MACs. MACs are not neccesarily designed to be good hashes (for a fixed key), because the threat model is different for them. They are designed so that you can't find a tag for a message for which you haven't seen a tag before. They are absolutely allowed to output two different tags for the same message or the same tag for two different messages (because an adversary could maybe have predicted a collision but not for which message pair).