Add support for a hw_timeout_multiplier system property.

In order to test the platform in emulators that are orders of magnitude
slower than real hardware we need to be able to avoid hitting timeouts
that prevent it from coming up properly. For this purpose introduce
a system property, ro.hw_timeout_multiplier, which may be set to
an integer value that acts as a multiplier for various timeouts on
the system.

Bug: 178231152
Change-Id: I6d7710beed0c4c5b1720e74e7abe3a586778c678
Ignore-AOSP-First: The frameworks/base part of this change conflicts with AOSP so we need to land it internally first