refactor: update CreateFilter function for header filters (#3779)

Inline headerFilterConfig to reduce function return params and reduce
complexity. Remove some test functions in favour of `assert` as it's
already implementing same functionality.

Use `any` instead of `interface{}` when possible just for less linters
suggesstions.

Follow up on #3778

Signed-off-by: Mustafa Abdelrahman <mustafa.abdelrahman@zalando.de>

Author: MustafaSaber

filters/builtin/compress_test.go

@@ -14,6 +14,7 @@ import (
 	"testing"
 	"time"
 
+	"github.com/stretchr/testify/assert"
 	"github.com/zalando/skipper/eskip"
 	"github.com/zalando/skipper/filters"
 	"github.com/zalando/skipper/filters/filtertest"
@@ -543,13 +544,7 @@ func TestCompress(t *testing.T) {
 				rsp.Header.Del("Content-Type")
 			}
 
-			if !compareHeaders(rsp.Header, ti.expectedHeader) {
-				printHeader(t, ti.expectedHeader, "invalid header", "expected")
-				printHeader(t, rsp.Header, "invalid header", "got")
-
-				t.Error("invalid header")
-				return
-			}
+			assert.Equal(t, ti.expectedHeader, rsp.Header)
 
 			if ok, err := compareBody(rsp, ti.contentLength); err != nil {
 				t.Error(err)

filters/builtin/decompress_test.go

@@ -32,6 +32,7 @@ func backend(t *testing.T, contentEncoding string, content io.Reader) *httptest.
 }
 
 func decompressingProxy(t *testing.T, backendURL string) *proxytest.TestProxy {
+	t.Helper()
 	routes := `
 		* -> decompress() -> "%s"
 	`