Lifecycle events called in wrong order

# Bug Report

**Ionic version:**
[x] **4.0.0**

**Current behavior:**
When changing the root page the lifecycle events of the previous and next page seem to fire out of order. So, lets say page A is currently displayed. Navigating to page B fires the lifecycle events in the following order:
1. Page B: ngOnInit
2. Page B: ionViewWillEnter
3. Page B: ionViewDidEnter
4. Page A: ngOnDestroy

(ionViewWillLeave and ionViewDidLeave do not fire at all)

**Expected behavior:**
I would expect that page A fires ngOnDestroy or ionViewWillLeave or ionViewDidLeave before page B's 'enter' events

Start by reproducing the reported navigation from page A to page B in Ionic 4.0.0 and log ngOnInit, ionViewWillEnter, ionViewDidEnter, ngOnDestroy, ionViewWillLeave, and ionViewDidLeave. Trace the lifecycle handling involved in root-page changes; done means the previous page's leave or destroy lifecycle occurs before the next page's enter events, with the expected callbacks firing.

Written by the indexing model from the issue text.