Revert^2 "Linker namespace configuration for the Runtime APEX."

This reverts commit 5bbd9b99.

Original change: This mimics the namespace configuration in
system/core/rootdir/etc/ld.config.txt so that the same namespace separation
between APEX and /system libraries is kept. The "default" namespace here
corresponds to "runtime" in the system config, and "platform" here
corresponds to "default" there.

Bug: 119867084
Bug: 113373927
Bug: 121149887
Change-Id: I9737a3c9425cfb5115091070ebf937b7c82142c7
Test: Flash and reboot device
Test: Run "/apex/com.android.runtime/bin/dex2oat -h" and check that libraries are loaded from right locations
Test: Run "adb shell cmd package compile -m speed-profile -f -a" with aosp/848510 to pick dex2oat in the APEX
Test: cts-tradefed run commandAndExit cts-dev -m CtsJniTestCases
Test: cts-tradefed run commandAndExit cts-dev -m CtsCompilationTestCases
Test: cts-tradefed run commandAndExit cts-dev -m CtsBionicTestCases (8 failures remain unchanged by this CL)