Fix the DiskReadViolation in GameManagerSettings

* Run the settings read in GameManagerService's handler as
  the thread calling from AM doesn't have IO permission.
* Replace the close with try-with-resources for stability,
  or we should close in the finally block instead.
* Fix the lazy init loading for the test.

Bug: 322221105
Flag: EXEMPT bugfix
Test: atest GameManagerServiceTests GameManagerServiceSettingsTests
Change-Id: Ic6227a607c71353e5f1c4c28ebe2a24c4c752935