[ISSUE #10208] Fix resource leak in IOTinyUtils.copyFile

[daguimu]

Problem

In IOTinyUtils.copyFile(), FileOutputStream and FileInputStream are created inline:

tc = new FileOutputStream(tf).getChannel();
sc = new FileInputStream(sf).getChannel();

The underlying stream references are lost. If new FileInputStream(sf) throws an exception (e.g., file locked), the already-created FileOutputStream and its channel will never be closed, leaking a file descriptor. The finally block only closes the FileChannel variables, which may be null at that point.

Root Cause

Stream objects are not stored in variables and therefore cannot be closed in the finally block if an exception occurs between their creation.

Fix

Refactored to use try-with-resources, which ensures all four resources (FileInputStream, FileOutputStream, and their channels) are properly closed in all cases:

try (FileInputStream fis = new FileInputStream(sf);
     FileOutputStream fos = new FileOutputStream(tf);
     FileChannel sc = fis.getChannel();
     FileChannel tc = fos.getChannel()) {
    sc.transferTo(0, sc.size(), tc);
}

Tests Added

No new tests needed — existing IOTinyUtilsTest.testCopyFile() covers the normal path and passes with the refactored code. The fix is a pure resource management improvement.

Impact

• No behavioral change for normal operation
• Fixes potential file descriptor leak on exception paths
• Reduces code from 14 lines to 5 lines with cleaner resource management

Fixes #10208