Fix dac_object_t::verify_type() implementation and uses

[LaurentiuCristofor]

I could no longer find a way to trigger an assert for an invalid id value.

Instead, I found this issue where get() and delete_row() methods would report a problem with ID '0' when called with an invalid id value. This was due to the verify_type() method, which would return id '0' as a way of indicating that the id could not be found. I changed the signature of the method and its uses to eliminate this issue.

[senderista]

This is a welcome fix, but also note that there are several other uses of report_invalid_object_id() that I consider semantically invalid and confusing to users. (See https://gaiaplatform.atlassian.net/browse/GAIAPLAT-1280.) Specifically, all 4 occurrences of this pattern in production/inc/gaia/direct_access/dac_object.inc are incorrect:

    if (!dac_base_t::exists())
    {
        report_invalid_object_id(gaia::common::c_invalid_gaia_id);
    }

The invalid_object_id exception thrown with c_invalid_gaia_id implies that the user supplied 0 as the ID (which is what they will see in the error message, not the c_invalid_gaia_id symbol). But this will be thrown when they dereference any gaia_ptr that may have been constructed with an ID that was valid at the time but has since been deleted (so the locator wrapped by the gaia_ptr contains c_invalid_gaia_offset in the current snapshot, triggering the exception when the locator is dereferenced).

We can certainly address this issue in a separate PR, of course.

[simone-gaia]

LGTM, but I wonder if it makes sense at all to let the user create an object with a known invalid ID. I'd rather throw an exception. If the user was not expecting an invalid ID the exception will stop execution: good. If the user was expecting an invalid ID he/she will have a try-catch.

[LaurentiuCristofor]

@vDonGlover : I am introducing this message to replace the "Cannot find an object with ID '0'." message, which is misleading, because this could also be thrown for objects that were initialized with valid IDs, but then were deleted.