ci(golangci-lint): update configuration and fix lint issues (#4247)

* ci: update golangci-lint configuration and lint settings

- Update golangci-lint to version 2
- Enable new linters and adjust existing ones
- Update lint settings across multiple test files
- Remove unused struct and variable checks
- Add new lint exclusions for generated code and specific directories

Signed-off-by: Flc <four_leaf_clover@foxmail.com>

* ci(github): update golangci-lint-action to v8 and lint version to v2.3.4

Signed-off-by: Flc <four_leaf_clover@foxmail.com>

* ci: downgrade golangci-lint to v2.1.6

Signed-off-by: Flc <four_leaf_clover@foxmail.com>

* ci(golangci): add gofumpt linter and fix related issues- Added gofumpt linter to .golangci.yml

Signed-off-by: Flc <four_leaf_clover@foxmail.com>

* test: ignore testifylint and gofumpt lints in specific test cases

Signed-off-by: Flc <four_leaf_clover@foxmail.com>

* build(deps): remove golang.org/x/lint

- Remove golang.org/x/lint package from go.mod
- Update related dependencies in go.sum

Signed-off-by: flc1125 <four_leaf_clover@foxmail.com>

* build(deps): downgrade golang.org/x/mod and golang.org/x/tools

- Downgrade golang.org/x/mod from v0.24.0 to v0.18.0
- Downgrade golang.org/x/tools from v0.33.0 to v.22.0

These changes are made to address compatibility issues with the current project setup.

Signed-off-by: flc1125 <four_leaf_clover@foxmail.com>

---------

Signed-off-by: Flc <four_leaf_clover@foxmail.com>
Signed-off-by: flc1125 <four_leaf_clover@foxmail.com>

gin_test.go

@@ -46,7 +46,7 @@ func setupHTMLFiles(t *testing.T, mode string, tls bool, loadMethod func(*Engine
 		})
 		router.GET("/raw", func(c *Context) {
 			c.HTML(http.StatusOK, "raw.tmpl", map[string]any{
-				"now": time.Date(2017, 07, 01, 0, 0, 0, 0, time.UTC),
+				"now": time.Date(2017, 07, 01, 0, 0, 0, 0, time.UTC), //nolint:gofumpt
 			})
 		})
 	})
@@ -883,7 +883,7 @@ func TestWithOptionFunc(t *testing.T) {
 type Birthday string
 
 func (b *Birthday) UnmarshalParam(param string) error {
-	*b = Birthday(strings.Replace(param, "-", "/", -1))
+	*b = Birthday(strings.ReplaceAll(param, "-", "/"))
 	return nil
 }