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

This reverts commit a0d9f2fd.

Original change: Needs to support e.g. app_process in "default" ->
libnativehelper in "runtime" -> platform libs in "default" -> libc etc in "runtime".

Always make sure to switch namespaces when switching library paths between
/system and the APEX, so that internal library dependencies in both
locations are loaded from their own directory. E.g. libc++ and libbase live
in both places, and their dependents must always load the version they were
compiled with.

This CL also adds a temporary workaround to not break hwasan builds
(b/121038155).

Bug: 119867084
Bug: 113373927
Bug: 121038155
Change-Id: I58d09ed091dd82b2162c4a0b51555174d9322e0e
Test: Flash and reboot device
Test: Remount / read-write, then on device: rm -f system/lib{,64}/lib{c,m,dl}.so; system/bin/dex2oat -h; stop && start
Test: mmma bionic/tests/ && adb root && adb shell rm -rf /data/nativetest\* && adb push out/target/product/taimen/data/nativetest* /data/ && adb shell /data/nativetest64/bionic-unit-tests/bionic-unit-tests && adb shell /data/nativetest/bionic-unit-tests/bionic-unit-tests
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)
Test: Patch internal; lunch taimen_hwasan-userdebug && m SANITIZE_TARGET=hwaddress && vendor/google/tools/flashall -w && adb shell /vendor/bin/sh -c ls