Regression test NPM Group to assure cooperation and cache

This is the testing ticket for PR https://github.com/sonatype/nexus-internal/pull/3831

Testing notes : 

• Test from branch (as we applied test before merge)
• Regression test NPM Group specifically https://docs.sonatype.com/pages/viewpage.action?pageId=124585108
• Added an extra credit section that should be minimally followed for this ticket: https://docs.sonatype.com/pages/viewpage.action?pageId=124585108#NPMTesting(NXRM3)-ExtraCredit:verifymultipleproxieshavingbeencachedinthegroup