Refactor locale number (#24134)

Before, the `GiteaLocaleNumber.js` was just written as a a drop-in
replacement for old `js-pretty-number`.

Actually, we can use Golang's `text` package to format.

This PR partially completes the TODOs in `GiteaLocaleNumber.js`:

> if we have complete backend locale support (eg: Golang "x/text"
package), we can drop this component.
> tooltip: only 2 usages of this, we can replace it with Golang's
"x/text/number" package in the future.

This PR also helps #24131

Screenshots:

<details>

![image](https://user-images.githubusercontent.com/2114189/232179420-b1b9974b-9d96-4408-b209-b80182c8b359.png)


![image](https://user-images.githubusercontent.com/2114189/232179416-14f36aa0-3f3e-4ac9-b366-7bd3a4464a11.png)

</details>

modules/translation/translation_test.go

@@ -0,0 +1,27 @@
+// Copyright 2023 The Gitea Authors. All rights reserved.
+// SPDX-License-Identifier: MIT
+
+package translation
+
+import (
+	"testing"
+
+	"code.gitea.io/gitea/modules/translation/i18n"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func TestPrettyNumber(t *testing.T) {
+	// TODO: make this package friendly to testing
+
+	i18n.ResetDefaultLocales()
+
+	allLangMap = make(map[string]*LangType)
+	allLangMap["id-ID"] = &LangType{Lang: "id-ID", Name: "Bahasa Indonesia"}
+
+	l := NewLocale("id-ID")
+	assert.EqualValues(t, "1.000.000", l.PrettyNumber(1000000))
+
+	l = NewLocale("nosuch")
+	assert.EqualValues(t, "1,000,000", l.PrettyNumber(1000000))
+}