refactor: retry file remove/rename when a file is busy and clean up os detection (#38588)

Rename functions "util.Remove" (remove.go) to "util.RemoveWithRetry"
(file_retry.go) and add comments to clarify their behaviors, also add
tests.

Refactor callers: when no concurrent access (cmd cli, migration, app
init, test), use "os.Xxx" directly.

More details are in `modules/util/file_retry.go`

By the way, clean up OS (windows) detection, make FileURLToPath test
always run

modules/util/path_test.go

@@ -7,7 +7,6 @@ import (
 	"net/url"
 	"os"
 	"path/filepath"
-	"runtime"
 	"testing"
 
 	"github.com/stretchr/testify/assert"
@@ -18,43 +17,46 @@ func TestFileURLToPath(t *testing.T) {
 	cases := []struct {
 		url      string
 		expected string
-		haserror bool
+		invalid  bool
 		windows  bool
 	}{
-		// case 0
 		{
-			url:      "",
-			haserror: true,
+			url:     "",
+			invalid: true,
 		},
-		// case 1
 		{
-			url:      "http://test.io",
-			haserror: true,
+			url:     "http://test.io",
+			invalid: true,
 		},
-		// case 2
 		{
 			url:      "file:///path",
 			expected: "/path",
 		},
-		// case 3
 		{
 			url:      "file:///C:/path",
 			expected: "C:/path",
 			windows:  true,
 		},
+		{
+			url:      "file:///z:/path",
+			expected: "z:/path",
+			windows:  true,
+		},
+		{
+			url:      "file:///path",
+			expected: "/path",
+			windows:  true,
+		},
 	}
 
-	for n, c := range cases {
-		if c.windows && runtime.GOOS != "windows" {
-			continue
-		}
+	for _, c := range cases {
 		u, _ := url.Parse(c.url)
-		p, err := FileURLToPath(u)
-		if c.haserror {
-			assert.Error(t, err, "case %d: should return error", n)
+		p, err := fileURLToPathInternal(u, c.windows)
+		if c.invalid {
+			assert.Error(t, err, "case %s: should return error", c.url)
 		} else {
-			assert.NoError(t, err, "case %d: should not return error", n)
-			assert.Equal(t, c.expected, p, "case %d: should be equal", n)
+			assert.NoError(t, err, "case %s: should not return error", c.url)
+			assert.Equal(t, c.expected, p, "case %s: should be equal", c.url)
 		}
 	}
 }
@@ -180,7 +182,7 @@ func TestCleanPath(t *testing.T) {
 	}
 
 	// for POSIX only, but the result is similar on Windows, because the first element must be an absolute path
-	if isOSWindows() {
+	if isOSWindows {
 		cases = []struct {
 			elems    []string
 			expected string