fix: Qiniuoss cannot upload non image attachments (#2331)

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#### What type of PR is this?

/kind bug

#### What this PR does / why we need it:

发现在七牛的 [QiniuOssFileHandler:145](f8bd4febb9/src/main/java/run/halo/app/handler/file/QiniuOssFileHandler.java (L145-L152)) 行中，如果文件不是图片类型的话就跳过了setThumbPath
但是在其他文件存储的handler中（如：本地 [LocalFileHandler:125](f8bd4febb9/src/main/java/run/halo/app/handler/file/LocalFileHandler.java (L125)), [TencentCosFileHandler:128](f8bd4febb9/src/main/java/run/halo/app/handler/file/TencentCosFileHandler.java (L128))）调用了handleImageMetadata default方法，该方法最后判断 thumbPath 为空时会将其设为 filePath
故在七牛云handler使用了handleImageMetadata 方法，使得其他类型文件也可以setThumbPath，并成功上传不会引发错误

#### Which issue(s) this PR fixes:

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Fixes #2320

#### Special notes for your reviewer:

看到其他文件handler中[TencentCosFileHandler:130](f8bd4febb9/src/main/java/run/halo/app/handler/file/TencentCosFileHandler.java (L130))有一个 `uploadResult.setThumbPath(fullPath);` 好像是没有必要的，也在[HuaweiObsFileHandler](f8bd4febb9/src/main/java/run/halo/app/handler/file/HuaweiObsFileHandler.java (L116-L123))中不存在上述代码。

#### Does this PR introduce a user-facing change?

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```release-note
修复了七牛云做附件存储时附件无法上传非图片文件的问题
```

src/main/java/run/halo/app/handler/file/QiniuOssFileHandler.java

@@ -142,14 +142,15 @@ public class QiniuOssFileHandler implements FileHandler {
             result.setMediaType(MediaType.valueOf(Objects.requireNonNull(file.getContentType())));
             result.setSize(file.getSize());
 
-            if (isImageType(file)) {
+            // Handle thumbnail
+            handleImageMetadata(file, result, () -> {
                 if (ImageUtils.EXTENSION_ICO.equals(pathDescriptor.getExtension())) {
-                    result.setThumbPath(fullPath);
+                    return fullPath;
                 } else {
-                    result.setThumbPath(StringUtils.isBlank(thumbnailStyleRule) ? fullPath :
-                        fullPath + thumbnailStyleRule);
+                    return StringUtils.isBlank(thumbnailStyleRule) ? fullPath :
+                        fullPath + thumbnailStyleRule;
                 }
-            }
+            });
 
             return result;
         } catch (IOException e) {