Removing SHA256 manifests from the tag listing

[Dramelac]

Official Docker registry doesn't list raw SHA256 manifest (cf. https://docker-docs.uclv.cu/registry/spec/api/#listing-image-tags). Tested on registry-1.docker.io.
In the current version of the serverless-registry, tag listing return tags but also sha256:[...] manifests that should be excluded.

I didn't find a way to directly query R2 with a more advance filter to exclude the sha256 manifest.
Instead I had to add a filter to remove them and a loop to find more tags until the n number of result are reach.

Bonus:

• I've also added a condition to only accept n > 0 to avoid any crash from the registry
• Now the Link for the next page is only supplied to the client if there is more result to fetch

[gabivlj]

We will need to run prettier and do some changes on the unit tests for these changes. Thanks for the contribution!

[Dramelac]

It should be good now, I've added tests to check if the SHA256 manifest are NOT included in the tag listing.