Add readiness and liveness probes in pingsource-mt-adapter

[airycanon]

Problem
The pingsource-mt-adapter currently lacks readiness and liveness probes.

Persona:
System Operator

Exit Criteria
Probes are implemented and correctly indicats the pingsource-mt-adapter is healthy.

[pierDipi]

Would you be interested in contributing this feature?
If you’re interested, I’d be happy to provide any additional information or resources you might need to get started. We have documentation available (development doc), and I’m also here or on CNCF Slack to answer any questions you might have.

/triage accepted
/help

[knative-prow]

@pierDipi:
This request has been marked as needing help from a contributor.

Please ensure the request meets the requirements listed here.

If this request no longer meets these requirements, the label can be removed
by commenting with the /remove-help command.

In response to this:

Would you be interested in contributing this feature?
If you’re interested, I’d be happy to provide any additional information or resources you might need to get started. We have documentation available (development doc), and I’m also here or on CNCF Slack to answer any questions you might have.

/triage accepted
/help

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