(...and ASSERT_NOT_REACHED => VERIFY_NOT_REACHED)
Since all of these checks are done in release builds as well,
let's rename them to VERIFY to prevent confusion, as everyone is
used to assertions being compiled out in release.
We can introduce a new ASSERT macro that is specifically for debug
checks, but I'm doing this wholesale conversion first since we've
accumulated thousands of these already, and it's not immediately
obvious which ones are suitable for ASSERT.
If it's missing we get an empty value, but we can't use that with
to_string_without_side_effects() so we have to use undefined as the
default.
Fixes#5142.
If we have a function as class extends value, we still cannot assume
that it has a prototype property and that property has a function or
null as its value - blindly calling to_object() on it may fail.
Fixes#5075.
Without this, the oss-fuzz build says:
../Userland/Libraries/LibJS/AST.cpp:58:34: error: member access into incomplete type 'const std::type_info'
return demangle(typeid(*this).name()).substring(4);
^
