[release/8.0-staging] Support IValidatableObject for nested model types in options source gen#94062

tarekgh merged 2 commits intorelease/8.0-stagingdotnet/runtime:release/8.0-stagingfrom

backport/pr-93952-to-release/8.0-stagingdotnet/runtime:backport/pr-93952-to-release/8.0-stagingCopy head branch name to clipboard