feat: allow searchbar to shrink when used in collapsible large title or fading header

# Bug Report

**Ionic version:**

[ ] **4.x**
[x] **5.x**

**Current behavior:**

Currently the searchbar just hides behind the header on scroll.

**Expected behavior:**

On native ios the searchbar is shrinking on scroll.
Also there is some opacity manipulation of placeholder and searchbar.

| ionic | ios notes |
| ------------- |-------------|
| | |