Integrate Entra profile photo with Jenkins avatar

[timja]

I lifted a fair bit of code from https://github.com/jenkinsci/avatar-plugin.

cc @janfaracik

Testing done

1. With profile photo configured in Entra ID - success
2. Without profile photo - success
3. Able to override Entra avatar with avatar plugin - success after Raise priority of this plugin in resolving avatars avatar-plugin#11

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