Add features test for cloud API key over data plane

[cretz]

Describe the solution you'd like

In this repo, when a TEMPORAL_CLIENT_CLOUD_API_KEY env var (set via org level GH secret of the same name) is present and non-empty, use it and TEMPORAL_CLIENT_NAMESPACE env var (set via org level GH var of the same name) to test against us-west-2.aws.api.temporal.io:7233 (can be put in env var too if we want). Specifically, the test should just run an execute workflow and should use a client with just the API key from a user POV, no manually set namespace headers.

Per-SDK Tickets

• Go - TODO
• Java - TODO
• Core - N/A
• TypeScript - TODO
• Python - TODO
• .NET - TODO
• Ruby - TODO
• PHP - TODO
• Temporal CLI - N/A