Problem: TermResponse deferred due to blocked autocommands lacks "data" payload.
Also, it may not fire if a new v:termresponse reuses the same string address.
Solution: add it. Use the value of v:termresponse for "data.sequence". Replace
pointer comparisons with a flag.
The removal of "old_termresponse" comparisons is required to pass the test on
the CI, or locally for me when compiled in RelWithDebInfo.
19379d1255