refactor: optimize getExternalProps with for-in loop and startsWith#4204

TrevorBurnham wants to merge 1 commit intocloudscape-design:maincloudscape-design/components:mainfrom

TrevorBurnham:perf/optimize-getexternalpropsTrevorBurnham/cloudscape-components:perf/optimize-getexternalpropsCopy head branch name to clipboard