Jetpack_WPCloud_SSO: Add new plugin

[tbradsha]

Closes MONOREP-149

As per request here: pdWQjU-1qh-p2

More discussion here: p1760537475717319-slack-C7YPW6K40

Proposed changes:

Other information:

• Have you written new tests for your changes, if applicable?
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Jetpack product discussion

Does this pull request change what data or activity we track or use?

Testing instructions:

• Go to '..'

[github-actions]

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Wpcloud Sso plugin:

No scheduled milestone found for this plugin.

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[mdbitz]

Thomas, I tested this out on Jurassic.Ninja and it looks good, what remaning steps are there to get an initial 0.1 version created?

[tbradsha]

I've rebased and fixed the lockfile, so if all passes, let's merge it!