[rush] Add stricter changefile validation to ensure changefiles target extant, correct projects. - #5715

[rush] Add stricter changefile validation to ensure changefiles target extant, correct projects.#5715

Ian Clanton-Thuon (iclanton) merged 18 commits into

microsoft:mainmicrosoft/rushstack:mainfrom

iclanton:stricter-rush-change-verificationiclanton/rushstack:stricter-rush-change-verificationCopy head branch name to clipboard