Add a check for upgrader_process_complete

## What problem would the enhancement address for VIP?

Because the contents of `/wp-content/plugins` and `/wp-content/themes` are setup as `read-only` directories, and end-users can't install or update plugins from within the `wp-admin`, the [hook `upgrader_process_complete`](https://developer.wordpress.org/reference/hooks/upgrader_process_complete/) will never run for either plugin install or update on the VIP Go platform.

When a VIP customer installs a plugin (via the [GitHub repo](https://docs.wpvip.com/technical-references/vip-codebase/)) with a function tied to that hook, their development team has to reverse engineer the plugin's code to execute that functionality.

This is not entirely unique to VIP, but only impacts WordPress environments where the `/wp-content/plugins` and `/wp-content/themes` are `read-only`, so it may not be a good fit for the [WordPress Coding Standards](https://github.com/WordPress-Coding-Standards/WordPress-Coding-Standards/).

## Describe the solution you'd like

A sniff that will flag places where the [`upgrader_process_complete` hook](https://developer.wordpress.org/reference/hooks/upgrader_process_complete/) is used. Preferably as an error because it is functionality that will not work.

## What code should be reported as a violation?

```
add_action( 'upgrader_process_complete', 'my_upgrade_function',10, 2);
```

## What code should *not* be reported as a violation?

I'm unaware of cases where this might be detected as a false positive.

## Additional context

_None applicable_

Bắt đầu bằng cách đọc các quy ước hiện có của repository về sniff và test, sau đó truy vết cách phát hiện các lệnh gọi đến hook upgrader_process_complete của WordPress. Issue cung cấp hook mục tiêu và một ví dụ add_action vi phạm; công việc được xem là hoàn tất khi sniff báo cáo việc sử dụng đó là một lỗi mà không xác định được trường hợp false positive nào.

Do mô hình lập chỉ mục viết ra từ nội dung của issue.