http_aws_sigv4: fix query normalization of %2b

Reported-by: Nuno Goncalves
Fixes #20543
Closes #20550

tests/unit/unit1979.c

@@ -83,6 +83,12 @@ static CURLcode test_unit1979(const char *arg)
       "/example space/",
       "/example%20space/"
     },
+    {
+      "get-plus-normalized",
+      true,
+      "/example+space/",
+      "/example%2Bspace/"
+    },
     {
       "get-slash-dot-slash-unnormalized",
       false,

tests/unit/unit1980.c

@@ -79,6 +79,11 @@ static CURLcode test_unit1980(const char *arg)
       "p3= &p1=+&p2=%20",
       "p1=%20&p2=%20&p3=%20"
     },
+    {
+      "2b-incoming",
+      "p3=%2b&p1=+",
+      "p1=%20&p3=%2B"
+    },
   };
 
   size_t i;