GCC 11 build fixes
Some files used std::numeric_limits without including <limits> and
failed to compile.
Some dynamic casts and calls to AndroidHardwareBufferExternalApi::
getInstance() produced nonnull warnings. Suppress these by
wrapping them in if statements.
Update Amber to suppress some new uninitialized variable warnings.
This commit also removes implicit-fallthrough from the list of ignored
GCC warnings in check_build_sanity.py. All such warnings in the CTS
should be fixed by now and recent versions of Clang also support
this warning.
Affects: All Amber tests
VK-GL-CTS issue: 2842
Change-Id: Id0d4e583b5c3bfab7b4c91c1c04372bcd55bac37