hvf: Makes assert_hvf_ok report failed expression

When a macOS Hypervisor.framework call fails which is checked by
assert_hvf_ok(), Qemu exits printing the error value, but not the
location
in the code, as regular assert() macro expansions would.

This change turns assert_hvf_ok() into a macro similar to other
assertions, which expands to a call to the corresponding _impl()
function together with information about the expression that failed
the assertion and its location in the code.

Additionally, stringifying the numeric hv_return_t code is factored
into a helper function that can be reused for diagnostics and debugging
outside of assertions.

Signed-off-by: Phil Dennis-Jordan <phil@philjordan.eu>
Message-ID: <20240605112556.43193-8-phil@philjordan.eu>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>