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/csv/csv_test.go

@@ -13,6 +13,7 @@ import (
 
 	"code.gitea.io/gitea/modules/git"
 	"code.gitea.io/gitea/modules/markup"
+	"code.gitea.io/gitea/modules/translation"
 
 	"github.com/stretchr/testify/assert"
 )
@@ -550,20 +551,6 @@ a|"he said, ""here I am"""`,
 	}
 }
 
-type mockLocale struct{}
-
-func (l mockLocale) Language() string {
-	return "en"
-}
-
-func (l mockLocale) Tr(s string, _ ...interface{}) string {
-	return s
-}
-
-func (l mockLocale) TrN(_cnt interface{}, key1, _keyN string, _args ...interface{}) string {
-	return key1
-}
-
 func TestFormatError(t *testing.T) {
 	cases := []struct {
 		err             error
@@ -591,7 +578,7 @@ func TestFormatError(t *testing.T) {
 	}
 
 	for n, c := range cases {
-		message, err := FormatError(c.err, mockLocale{})
+		message, err := FormatError(c.err, &translation.MockLocale{})
 		if c.expectsError {
 			assert.Error(t, err, "case %d: expected an error to be returned", n)
 		} else {