Support disabled resolved stub server mode (#1493)

In the case of disabled stub listeren the list of name servers is unordered. The solution is to configure the resolv.conf file directly instead of dbus API.
Because third-party services also can manipulate the DNS settings the agent watch the resolv.conf file and keep it up to date.

- apply file type DNS manager if in the name server list does not exist the 127.0.0.53 address
- watching the resolv.conf file with inotify service and overwrite all the time if the configuration has changed and it invalid
- fix resolv.conf generation algorithm

client/internal/dns/file_linux_test.go

@@ -1,3 +1,5 @@
+//go:build !android
+
 package dns
 
 import (
@@ -7,7 +9,7 @@ import (
 
 func Test_mergeSearchDomains(t *testing.T) {
 	searchDomains := []string{"a", "b"}
-	originDomains := []string{"a", "b"}
+	originDomains := []string{"c", "d"}
 	mergedDomains := mergeSearchDomains(searchDomains, originDomains)
 	if len(mergedDomains) != 4 {
 		t.Errorf("invalid len of result domains: %d, want: %d", len(mergedDomains), 4)
@@ -49,6 +51,67 @@ func Test_mergeSearchTooLongDomain(t *testing.T) {
 	}
 }
 
+func Test_isContains(t *testing.T) {
+	type args struct {
+		subList []string
+		list    []string
+	}
+	tests := []struct {
+		args args
+		want bool
+	}{
+		{
+			args: args{
+				subList: []string{"a", "b", "c"},
+				list:    []string{"a", "b", "c"},
+			},
+			want: true,
+		},
+		{
+			args: args{
+				subList: []string{"a"},
+				list:    []string{"a", "b", "c"},
+			},
+			want: true,
+		},
+		{
+			args: args{
+				subList: []string{"d"},
+				list:    []string{"a", "b", "c"},
+			},
+			want: false,
+		},
+		{
+			args: args{
+				subList: []string{"a"},
+				list:    []string{},
+			},
+			want: false,
+		},
+		{
+			args: args{
+				subList: []string{},
+				list:    []string{"b"},
+			},
+			want: true,
+		},
+		{
+			args: args{
+				subList: []string{},
+				list:    []string{},
+			},
+			want: true,
+		},
+	}
+	for _, tt := range tests {
+		t.Run("list check test", func(t *testing.T) {
+			if got := isContains(tt.args.subList, tt.args.list); got != tt.want {
+				t.Errorf("isContains() = %v, want %v", got, tt.want)
+			}
+		})
+	}
+}
+
 func getLongLine() string {
 	x := "search "
 	for {