PR to Merge MVB code changes to Main.

[supreethmr]

Summary

This PR contains below PR changes which are grouped to release as MVB.

• PR to Update Webpack DevServer version from 3 to 4 in webpack-config-terra and terra-functional-testing : https://github.com/cerner/terra-toolkit/pull/725
• PR to Add Upgrade Guide for Terra-Functional-Testing to provide information about breaking changes of updating webpack-devserver to version 4 : https://github.com/cerner/terra-toolkit/pull/741
• PR to Drop React Intl V2 V3 support from terra-aggregate-translations : https://github.com/cerner/terra-toolkit/pull/739

This changes has been verified with open source and internal projects of UX framework.

Additional Details

@cerner/terra