Configuration as code plugin support

[timja]

Hi 👋

It looks like this plugin doesn't support the configuration-as-code plugin,

Would it be possible to support this?

Here's the guide:
https://github.com/jenkinsci/configuration-as-code-plugin/blob/master/docs/PLUGINS.md

This class needs some updates:
https://github.com/jenkinsci/fortify-on-demand-uploader-plugin/blob/master/src/main/java/org/jenkinsci/plugins/fodupload/FodGlobalDescriptor.java#L19

and ideally a test confirming all is working (testing guide is included in the above doc)