Backtrace collection is relatively expensive and can significantly slow
down malloc()-heavy code when mcheck is enabled.
Add a new CONFIG_MCHECK_BACKTRACE option (default y) to allow disabling
backtrace collection while keeping the other mcheck features (canaries,
double-free detection, etc.) enabled. This allows using mcheck with less
overhead when caller information is not needed.
Co-developed-by: Claude <noreply@anthropic.com>
Signed-off-by: Simon Glass <simon.glass@canonical.com>