REGTESTS: Add sample_fetches/cook.vtc

Add a reg-test verifying the fix in dea7c209f8a77b471323dd97bdc1ac4d7a17b812.

Some parts of the configuration used in the were taken from the initial bug
report from Maciej.

Should be backported together with dea7c209f8a77b471323dd97bdc1ac4d7a17b812
(all stable versions).

Co-authored-by: Maciej Zdeb <maciej@zdeb.pl>

reg-tests/sample_fetches/cook.vtc

@@ -0,0 +1,37 @@
+varnishtest "cook sample fetch Test"
+
+feature ignore_unknown_macro
+
+server s1 {
+    rxreq
+    txresp
+} -start
+
+haproxy h1 -conf {
+    defaults
+        mode http
+
+    frontend fe
+        bind "fd@${fe}"
+        http-request set-var(txn.count) req.cook_cnt()
+        http-request set-var(txn.val) req.cook_val()
+        http-request set-var(txn.val_cook2) req.cook_val(cook2)
+        http-response set-header count %[var(txn.count)]
+        http-response set-header val %[var(txn.val)]
+        http-response set-header val_cook2 %[var(txn.val_cook2)]
+
+        default_backend be
+
+    backend be
+        server srv1 ${s1_addr}:${s1_port}
+} -start
+
+client c1 -connect ${h1_fe_sock} {
+    txreq -url "/" \
+        -hdr "cookie: cook1=0; cook2=123; cook3=22"
+    rxresp
+    expect resp.status == 200
+    expect resp.http.count == "3"
+    expect resp.http.val == "0"
+    expect resp.http.val_cook2 == "123"
+} -run