Add readiness probes

[mtparet]

What was changed

Adding readiness probes to web and server deployment.

Why?

Currently we send requests to these pods even when these are not fully started. These basic readiness should help wait before sending requests that temporal is up.

Checklist

1. Closes #710

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[VLZZZ]

Hey team, Is this going to be reviewed/merged anytime soon?

We experiencing drops anytime we upgrade Temporal cluster with multiple replicas. While we're following RollingUpdate strategy and rolling out performed 1 by 1, I've noticed that pod immediately reaches Ready status while logs still states that: "operation":"PollActivityTaskQueue","wf-namespace":"<redacted>","error":"Frontend is not healthy yet"

And only several seconds (or faster) later Frontend is now healthy

Under the heavy load we encountering too many rejects which affecting performance when using Temporal

Thank you!