Replace PR workflow with a release draft.

[dblock]

Description

I propose we replace the checked in ../builds/OpenSearch.latest.yaml with a release draft workflow.

Here's what it produces: https://github.com/dblock/opensearch-api-specification/releases/tag/latest-draft-release

This avoids having to have another PR behind every change to update the spec, and lets you have separate builds per branch.

Note coverage in this PR is failing because I moved builds -> build.

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.
For more information on following Developer Certificate of Origin and signing off your commits, please check here.

[nhtruong]

Looks good to me.
Would we be able to pull the ./build/Opensearch.latest.yaml file with a curl command while it's still in draft release? It'll be useful to be able to do that and test the changes with a client generator before finalizing the release.

[dblock]

Would we be able to pull the ./build/Opensearch.latest.yaml file with a curl command while it's still in draft release? It'll be useful to be able to do that and test the changes with a client generator before finalizing the release.

Yes, try https://github.com/dblock/opensearch-api-specification/releases/download/latest-draft-release/OpenSearch.latest.yaml

[dblock]

Closing in favor of #213.