Revert^2 "Load boot image at a random address."

This reverts commit f3d07737.

Fixed Heap constructor to reserve extra space for GSS.

Change-Id: I6a65be35f4aa183304db5491da4a4810d8e3b266
Test: m test-art-host-gtest
Test: testrunner.py --host --optimizing --relocate --no-relocate
Test: Pixel 2 XL boots.
Test: m test-art-target-gtest
Test: testrunner.py --target --optimizing --relocate --no-relocate
Test: art/test/testrunner/run_build_test_target.py -j48 art-gtest-gss-gc-tlab
Bug: 77856493