improve the performance of applying the query parameters

* improve the loging by adding the query parameters from the request first, then adding the parameters from the client and skip if already exists
* additional unit tests for the query parameters

```shell
% go test -benchmem -bench=. -run=^Benchmark
goos: darwin
goarch: amd64
pkg: github.com/go-resty/resty/v2
cpu: Intel(R) Core(TM) i9-9880H CPU @ 2.30GHz
Benchmark_parseRequestURL_QueryParams-16         1000000              1158 ns/op             352 B/op          9 allocs/op
PASS
ok      github.com/go-resty/resty/v2    2.473s
```

middleware.go

@@ -134,32 +134,31 @@ func parseRequestURL(c *Client, r *Request) error {
 	}
 
 	// Adding Query Param
-	query := make(url.Values)
-	for k, v := range c.QueryParam {
-		for _, iv := range v {
-			query.Add(k, iv)
+	if l := len(c.QueryParam) + len(r.QueryParam); l > 0 {
+		query := make(url.Values, l)
+		for k, v := range r.QueryParam {
+			query[k] = v[:]
 		}
-	}
 
-	for k, v := range r.QueryParam {
-		// remove query param from client level by key
-		// since overrides happens for that key in the request
-		query.Del(k)
+		for k, v := range c.QueryParam {
+			// skip query parameter if it was set from request
+			if _, ok := query[k]; ok {
+				continue
+			}
 
-		for _, iv := range v {
-			query.Add(k, iv)
+			query[k] = v[:]
 		}
-	}
 
-	// GitHub #123 Preserve query string order partially.
-	// Since not feasible in `SetQuery*` resty methods, because
-	// standard package `url.Encode(...)` sorts the query params
-	// alphabetically
-	if len(query) > 0 {
-		if IsStringEmpty(reqURL.RawQuery) {
-			reqURL.RawQuery = query.Encode()
-		} else {
-			reqURL.RawQuery = reqURL.RawQuery + "&" + query.Encode()
+		// GitHub #123 Preserve query string order partially.
+		// Since not feasible in `SetQuery*` resty methods, because
+		// standard package `url.Encode(...)` sorts the query params
+		// alphabetically
+		if len(query) > 0 {
+			if IsStringEmpty(reqURL.RawQuery) {
+				reqURL.RawQuery = query.Encode()
+			} else {
+				reqURL.RawQuery = reqURL.RawQuery + "&" + query.Encode()
+			}
 		}
 	}
 

middleware_test.go

@@ -200,13 +200,32 @@ func Test_parseRequestURL(t *testing.T) {
 					"foo": "1", // ignored, because of the "foo" parameter in request
 					"bar": "2",
 				})
-				c.SetQueryParams(map[string]string{
+				r.SetQueryParams(map[string]string{
 					"foo": "3",
 				})
 				r.URL = "https://example.com/"
 			},
 			expectedURL: "https://example.com/?foo=3&bar=2",
 		},
+		{
+			name: "adding query parameters by request to URL with existent",
+			init: func(c *Client, r *Request) {
+				r.SetQueryParams(map[string]string{
+					"bar": "2",
+				})
+				r.URL = "https://example.com/?foo=1"
+			},
+			expectedURL: "https://example.com/?foo=1&bar=2",
+		},
+		{
+			name: "adding query parameters by request with multiple values",
+			init: func(c *Client, r *Request) {
+				r.QueryParam.Add("foo", "1")
+				r.QueryParam.Add("foo", "2")
+				r.URL = "https://example.com/"
+			},
+			expectedURL: "https://example.com/?foo=1&foo=2",
+		},
 	} {
 		t.Run(tt.name, func(t *testing.T) {
 			c := New()