Rename OverviewProxyService to LauncherProxyService

- OverviewProxyService is a shared service to send information from SysUI to Launcher, only 1 method `onOverviewShown` is related to Overview, renaming this service to better reflect the nature to avoid bugs misrouted to Overview component.

Fix: 391563516
Test: presubmit
Flag: EXEMPT REFACTOR
Change-Id: Idc7b085a965c77fae5c9271005771c2eef65674b