bug: collapsible large title should snap between expanded and collapsed when released in between states

# Bug Report

**Ionic version:**

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

**Current behavior:**

Currently, the ios large (collapse) header is able to be between the two states when releasing the pointer via scroll. It then looks like:


**Expected behavior:**

As far as i see, native it switches either to the expanded or collapsed state, determined by how far the transition was done when releasing.

No file, test, or entry point is named in the issue. Start by locating the iOS large-title or collapsible-header implementation and reproduce releasing the scroll between states; done means it consistently settles at either the expanded or collapsed state according to transition progress, with regression coverage.

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