zephyr/ztest_assert.h: Fix implicit to bool conversion

The current zassert macro uses implicit conversion to boolean which
has implication on analysis tools like clang-tidy-14. This add an
aditional step to create a boolean value for the evaluation instead
use the string direct which allows run analysis tool without this
warning/error.

Signed-off-by: Gerson Fernando Budke <nandojve@gmail.com>