[feature] Implement IMAP protocol support

[zuobiao-zhou]

What's changed?

The IMAP protocol, also known as the Internet Message Access Protocol, is similar to the POP3 protocol and can be used to monitor mailbox information. However, the IMAP protocol provides users with a more convenient and reliable experience because it can monitor more detailed mailbox information, including specific information under each folder in the mailbox.

This PR implements support for the IMAP protocol and provides monitoring templates for QQ email and NetEase email

It should be noted that in order to implement Java's support for UTF-7 encoding, a third-party package com.beetstra.utf7 has been introduced, which uses the MIT License.

I will add ut and help doc later.

Checklist

• [x] I have read the Contributing Guide
• [x] I have written the necessary doc or comment.
• [x] I have added the necessary unit tests and all cases have passed.

Add or update API

• [ ] I have added the necessary e2e tests and all cases have passed.

[zuobiao-zhou]

All tasks have been completed.

[tomsun28]

👍lgtm! Recommended that merge this after releasing version 1.6.0.