Test that SIGINT interrupts non-terminating goals on unix.

Cleanup: use tokio::test instead of special test helpers

Added pty_exec.py helper script to run binaries with a pseudoterminal attached (bug won't trigger otherwise).

Tested CI to fail on all unixes (ubuntu+macos) with older rustyline, and pass with new one.

tests-pl/issue-interrupt-nontermination.pl

@@ -0,0 +1,38 @@
+% Server
+:- use_module(library(process)).
+:- use_module(library(charsio)).
+:- use_module(library(lists)).
+:- use_module(library(time)).
+
+prolog_path(Prolog) :-
+    read(Body),
+    term_variables(Body, [Prolog]),
+    Body.
+
+main :-
+    prolog_path(Prolog),
+    CMD = "\
+use_module(library(os)), \
+pid(PID), \
+write(PID), nl, \
+asserta((f :- f)), \
+catch(f, Err, (write(Err),nl)), \
+write(done), nl, \
+halt.",
+    process_create("tests-pl/pty_exec.py", [Prolog, "-g", CMD], [stdout(pipe(O))]),
+    get_line_to_chars(O, PID0, ""),
+    append(PID, "\r\n", PID0),
+    process_create("kill", ["-s", "INT", PID], []),
+    sleep(5),
+    % second kill should fail because process should exit after one kill
+    process_create("kill", ["-s", "INT", PID], [stderr(null), process(PK)]),
+    process_wait(PK, Status),
+    status_report(Status, PID), nl.
+
+status_report(exit(1), _PID) :- write(ok).
+status_report(exit(0), PID) :-
+    write(not_dead),
+    % kill by force to exit cleanly
+    process_create("kill", ["-9", PID], []).
+
+:- initialization(main).