Support other KMS keys besides GCP

[haydentherapper]

Description

Very trivial change, we just need to update

rekor/pkg/signer/signer.go

Line 27 in a90366e

func New(ctx context.Context, signer string, pass string) (signature.Signer, error) {

to load all KMS providers and fetch the key with kms.Get (fulcio example)

[jbgcarnes]

This feature would help me for sure. If the project open to an MR about it?

[haydentherapper]

Feel free to fix this issue, thanks! It should be straightforward.

[bobcallaway]

This will have a pretty dramatic increase in the dependency footprint for Rekor, but the fix is pretty straightforward.

[jtcarnes]

Sorry, family health crisis. Taken care of now. I'll push it out in a week or so.