async_hooks: rename PromiseWrap.parentId

Rename the `parentId` property on the PromiseWrap object to a
`isChainedPromise` property. The former wasn't quite useful as it was
always defined to be the same value as the trigger id available in the
init hook. Instead rename the property to be closer to the information
it communicates: whether the promise is a chained promise or not.

PR-URL: https://github.com/nodejs/node/pull/18633
Fixes: https://github.com/nodejs/node/issues/18470


Reviewed-By: Andreas Madsen <amwebdk@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Tiancheng "Timothy" Gu <timothygu99@gmail.com>