Rename IMM#mServedInputConnectionWrapper to IMM#mServedInputConnection

This is a mechanical refactoring CL that renames

  InputMethodManager#mServedInputConnectionWrapper

to

  InputMethodManager#mServedInputConnection,

which is supposed to be still understandable and describes what it is.

This is a preparation for upcoming remanings e.g.:

 * IInputContext -> IInputConnection
 * IInputContextInvoker -> IInputConnectionInvoker
 * IInputConnectionWrapper -> RemotableInputConnection

Bug: 192412909
Test: presubmit
Change-Id: Icf213cff4cb6d571e5a09040feb9d24c9f1665d1