After using the new vector stuff for real I found...

A bug in AST_VECTOR_INSERT_AT that could cause a seg fault.

The callbacks needed to be closer to ao2_callback in behavior
WRT to CMP_MATCH and CMP_STOP behavior and the ability to return
a vector of matched entries.

A pre-existing issue with APPEND and REPLACE was also fixed.

I also added a new macro to test.h that acts like ast_test_validate
but also accepts a return code variable and a cleanup label.  As well
as printing the error, it sets the rc variable to AST_TEST_FAIL and
does a goto to the specified label on error.  I had a local version
of this in test_vector so I just moved it.

ASTERISK-25045

Change-Id: I05e5e47fd02f61964be13b7e8942bab5d61b29cc