[hwasan] Tweak process and thread initialization.

Make sure that TLS_SLOT_TSAN is always available and correctly set up in
HWASan-instrumented functions by setting up the tls register and running hwasan
initialization (__hwasan_init in the main thread and __hwasan_thread_enter in
secondary) early enough.

This is needed to accomodate a change in HWASan: https://reviews.llvm.org/D52249

Bug: 112438058
Test: boot with SANITIZE_TARGET=hwaddress, run bionic-tests
Change-Id: Icd909a4ea0da6c6c1095522bcc28debef5f2c63d