WATCH no longer ignores keys which have expired for MULTI/EXEC. (#7920)

This wrong behavior was backed by a test, and also documentation, and dates back to 2010.
But it makes no sense to anyone involved so it was decided to change that.

Note that 20eeddf (invalidate watch on expire on access) was released in 6.0 RC2
and 2d1968f released in in 6.0.0 GA (invalidate watch when key is evicted).
both of which do similar changes.

(cherry picked from commit 556acefe7556443b6d1741d804add92047bf4a8b)

src/expire.c

@@ -64,7 +64,7 @@ int activeExpireCycleTryExpire(redisDb *db, dictEntry *de, long long now) {
             dbSyncDelete(db,keyobj);
         notifyKeyspaceEvent(NOTIFY_EXPIRED,
             "expired",keyobj,db->id);
-        trackingInvalidateKey(NULL,keyobj);
+        signalModifiedKey(NULL, db, keyobj);
         decrRefCount(keyobj);
         server.stat_expiredkeys++;
         return 1;

tests/unit/multi.tcl

@@ -221,7 +221,7 @@ start_server {tags {"multi"}} {
         r exec
     } {}
 
-    test {WATCH will not consider touched expired keys} {
+    test {WATCH will consider touched expired keys} {
         r del x
         r set x foo
         r expire x 1
@@ -230,7 +230,7 @@ start_server {tags {"multi"}} {
         r multi
         r ping
         r exec
-    } {PONG}
+    } {}
 
     test {DISCARD should clear the WATCH dirty flag on the client} {
         r watch x