Align the boot dexopt pass in the legacy code with ART Service.

A preparation to call into ART Service for that in a later CL.

- Add new compilation reason boot-after-mainline-update.

- Set the reason before doing anything else. This bit will be in the
  ART Service code path as well.

- Remove the dexopt_system_ui_on_boot device config property, because
  ART Service won't support it.

- The selection and priority of the packages in OTA upgrade dexopt are
  still different for now.

Test: atest CtsCompilationTestCases
Bug: 251903639
Bug: 265685704
Change-Id: Ie3c000918a0024f768972f9c8c171cd6f0e029f5