[RESTRICT AUTOMERGE] Stay in app pinned mode upon SystemUI crash

Bug: b/366405211
Test: atest LockTaskControllerTest.java
Flag: EXEMPT BUGFIX
(cherry picked from commit 575845147cb48d71893f12665bae2e8892aa7e06)
Cherrypick-From: https://googleplex-android-review.googlesource.com/q/commit:8a0f8df37587f1677cc6ab80a567d8f82ff78121
Merged-In: Ia9f54b229b998e29da53436ed6ed64214903724c
Change-Id: Ia9f54b229b998e29da53436ed6ed64214903724c
6 files changed