Move dumpOatRules to platform_bootclasspath

Bug: 177892522
Test: m oat-dump-boot
      - test output to make sure that this change does not change the
        generated files, at least no more than no changes do as the
	output from this rule is not deterministic. See b/186459873.

Change-Id: Ib2b4203d9bb1fd0ee9443aee4e58b54b38b491cf