Refactoring performAccessibilityShortcut

Internal function (managerService) was already paramaterized.
Paramaterizing external function (manager) allows us to clean up code
from AccessibilityTarget, and will help with expandability in the future.

Test: atest com.android.server.accessibility
Flag: EXEMPT internal refactoring
Bug: 330775538
Change-Id: I5419dc1a5b70bdb8c208c2222bf997be16aff746