Refactor legacy unknwon/com package, improve golangci lint (#19284)

The main purpose is to refactor the legacy `unknwon/com` package.
1. Remove most imports of `unknwon/com`, only `util/legacy.go` imports the legacy `unknwon/com`
2. Use golangci's depguard to process denied packages
3. Fix some incorrect values in golangci.yml, eg, the version should be quoted string `"1.18"`
4. Use correctly escaped content for `go-import` and `go-source` meta tags
5. Refactor `com.Expand` to our stable (and the same fast) `vars.Expand`, our `vars.Expand` can still return partially rendered content even if the template is not good (eg: key mistach).

modules/templates/vars/vars_test.go

@@ -0,0 +1,72 @@
+// Copyright 2022 The Gitea Authors. All rights reserved.
+// Use of this source code is governed by a MIT-style
+// license that can be found in the LICENSE file.
+
+package vars
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func TestExpandVars(t *testing.T) {
+	kases := []struct {
+		tmpl  string
+		data  map[string]string
+		out   string
+		error bool
+	}{
+		{
+			tmpl: "{a}",
+			data: map[string]string{
+				"a": "1",
+			},
+			out: "1",
+		},
+		{
+			tmpl: "expand {a}, {b} and {c}, with non-var { } {#}",
+			data: map[string]string{
+				"a": "1",
+				"b": "2",
+				"c": "3",
+			},
+			out: "expand 1, 2 and 3, with non-var { } {#}",
+		},
+		{
+			tmpl: "中文内容 {一}, {二} 和 {三} 中文结尾",
+			data: map[string]string{
+				"一": "11",
+				"二": "22",
+				"三": "33",
+			},
+			out: "中文内容 11, 22 和 33 中文结尾",
+		},
+		{
+			tmpl: "expand {{a}, {b} and {c}",
+			data: map[string]string{
+				"a": "foo",
+				"b": "bar",
+			},
+			out:   "expand {{a}, bar and {c}",
+			error: true,
+		},
+		{
+			tmpl:  "expand } {} and {",
+			out:   "expand } {} and {",
+			error: true,
+		},
+	}
+
+	for _, kase := range kases {
+		t.Run(kase.tmpl, func(t *testing.T) {
+			res, err := Expand(kase.tmpl, kase.data)
+			assert.EqualValues(t, kase.out, res)
+			if kase.error {
+				assert.Error(t, err)
+			} else {
+				assert.NoError(t, err)
+			}
+		})
+	}
+}