feat(compute): add --reverse-dns flag to create command

[nhedger]

Note

Disclosure:

• AI assistance was used to implement this feature
• Manual review and testing was done

Description

Closes #564

This PR adds a --reverse-dns flag to the compute instance create command.

The implementation follows the same approach already used by compute instance update: after the instance is created and the operation completes successfully, the CLI applies reverse DNS through the dedicated reverse-DNS API endpoint before returning the final instance output.

Test coverage was added for both the CLI surface and the API-backed lifecycle:

• a without-API testscript scenario checks that compute instance create --help exposes --reverse-dns
• a with-API testscript scenario creates an instance with reverse DNS, verifies it via compute instance show, then deletes it
  One API detail worth noting is that the returned reverse DNS value includes a trailing dot, so the API test matches that behavior.

Checklist

(For exoscale contributors)

• Changelog updated (under Unreleased block, and add the Pull Request #number for each bit you add to the CHANGELOG.md)
• Testing

Testing

• go build -mod=vendor -o bin/exo .
• go test ./cmd/...
• go test -C tests/e2e -run 'TestScriptsLocal/compute_instance_create_flags' -v
• go test -C tests/e2e -tags=api -run 'TestScriptsAPI/instance_create_reverse_dns' -v