[JENKINS-74028] Extract inline script from choiceParameterCommon.jelly

[yaroslavafenkin]

https://issues.jenkins.io/browse/JENKINS-74028

Testing done

Created a freestyle project with 2 Active Choices Parameters. Took sample Groovy scripts from the README. Choice type - Multi Select.

Before the change
After the change

P.S. On the After the change video you'll see CSP violations in the report. Those aren't related to this change, and are fixed in #371. The reason they didn't appear on the Before video is because it was recorded with the plugin version built from #371.

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