Add new resource sentry_release_deployment

[mvantellingen]

This resource creates a new deployment for a specific release and environment in sentry.

[jianyuan]

@mvantellingen I'm getting a 404 error when I run your test locally. I think we need a sentry_release resource and data source too.

From the source code, the create release deployment endpoint is checking to see if a release of a particular version exists.

I'm happy to merge this PR as is on the assumption that a release was created elsewhere. What do you think?

[mvantellingen]

@jianyuan what we do (and I assume is the most common scenario) is build the release artifacts with for example a GitHub action, create the release also with a GitHub action and then do the actual deployment using Terraform.

I'm not sure there is a valid use-case for creating releases with Terraform

[mvantellingen]

@jianyuan I merged your suggestion. Anything else I can do to help get this released? If you need some time available for this then no worries.