Support separating A11yManagers by device id

An AccessibilityManagerClient is now associated with a device id.
Usually this is the default device (phone), but if a proxy is
registered for a display that belongs to a virtual device, a client
will be assosiated with that device's id, and updates will happen
based on state held by the ProxyManager.

When broadcasting to Clients, check the device id.

Clients are "moved" back to the
default device and updated with the current user state if
1. the virtual device is closed or 2.a proxy is unregistered and
there are no more active proxies belonging to that device.

onProxyChanged behaves like onClientChanged/onUserStateChanged to update
the clients and some system state (like updating window tracking). All
IAccessibilityManagerClient methods (except setUiContrast) are called
by ProxyManager.

Additional changes:

- Remove onProxyChanged/onClientChanged in ProxyManager#registerProxy.
Inform apps of a new proxy after the proxy's installed and enabled
service infos have propagated (in ProxyA11yServiceConnection).
- Call A11yInputFilter from the main thread, since it's not thread
safe.
- Add more dump logging

See video in the comments

Bug: 254545943
Test: atest AccessibilityDisplayProxyTest
Change-Id: If4be657d9fe7a3cdba1437a1f2433b3fab5193b6