jjbb: multibranch pipeline to validate ironbank docker context

[v1v]

What does this PR do?

Create Jenkins Multibranch Pipeline for the Validate Ironbank docker context which will run periodically.

Why is it important?

#32954 was recently merged, though the docker context validation is not part of the docker context generation.

The validation will run periodically to validate if the manifest has changed, that was agreed in a private GitHub issue

This PR won't be tested in the CI, except whether the JJBB is correct as part of the pre-commit validation.

The implementation will be done in a follow up

[elasticmachine]

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• Start Time: 2022-09-05T12:10:40.876+0000

• Duration: 12 min 6 sec

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Passed	3
Skipped	0
Total	3

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