Add support for GMAIL POP3 OAUTH2

Feature request
1

While eM Client supports OAUTH2 with GMail configured with IMAP, POP3 GMail support has less security. For GMail POP3 support, the eM Client only supports application passwords. This was tested with eM Client version 10.3.1738 on Windows 10.

This is a request to add OAUTH2 support for POP3 GMail users.

For developer reference and proof of support, see:

2

The latest build V10.3.4341 as per the announcement today now has Gmail POP3 OAuth support

Quote: - * POP3 with OAuth for Microsoft 365 and Gmail (via manual setup)