Add `tryIndexFromEnd()` function#1219

SteveL-MSFT merged 4 commits intoPowerShell:mainPowerShell/DSC:mainfrom

Gijsreyn:gh-57/main/add-tryindexfromend-functionGijsreyn/operation-methods:gh-57/main/add-tryindexfromend-functionCopy head branch name to clipboard