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/runtime.go

@@ -5,6 +5,8 @@ package util
 
 import "runtime"
 
+const isOSWindows = runtime.GOOS == "windows"
+
 func CallerFuncName(optSkipParent ...int) string {
 	pc := make([]uintptr, 1)
 	skipParent := 0