Dependencies: Update selected dependencies to latest major versions

[NguyenThuyLan]

Prerequisites

• I have added steps to test this contribution in the description below

If there's an existing issue for this PR then this fixes

Description

Update outdated dependencies to their latest major versions as part of the v18 release cycle.

Changes:

• Updated the following packages in Directory.Packages.props:

  • Serilog.Extensions.Hosting
  • Serilog.Settings.Configuration
  • Serilog.AspNetCore
  • Markdig
  • MailKit
  • Microsoft.CodeAnalysis.CSharp

• Added Microsoft.CodeAnalysis.CSharp.Workspaces to Directory.Packages.props in tests to resolve version conflicts caused by the Microsoft.CodeAnalysis.CSharp upgrade.

Notes

How to test

• Build the solution
• Run all unit and integration tests

[github-actions]

Hi there @NguyenThuyLan, thank you for this contribution! 👍

While we wait for one of the Core Collaborators team to have a look at your work, we wanted to let you know about that we have a checklist for some of the things we will consider during review:

• It's clear what problem this is solving, there's a connected issue or a description of what the changes do and how to test them
• The automated tests all pass (see "Checks" tab on this PR)
• The level of security for this contribution is the same or improved
• The level of performance for this contribution is the same or improved
• Avoids creating breaking changes; note that behavioral changes might also be perceived as breaking
• If this is a new feature, Umbraco HQ provided guidance on the implementation beforehand
• 💡 The contribution looks original and the contributor is presumably allowed to share it

Don't worry if you got something wrong. We like to think of a pull request as the start of a conversation, we're happy to provide guidance on improving your contribution.

If you realize that you might want to make some changes then you can do that by adding new commits to the branch you created for this work and pushing new commits. They should then automatically show up as updates to this pull request.

Thanks, from your friendly Umbraco GitHub bot 🤖 🙂

[AndyButland]

As we've discussed, we've had some problems here in getting NUnit and the NUnit test adapter to upgrade, as somewhere within those changes there's something that triggers a problem with the integration tests running on the AzureDevOps pipeline. One group - 3 of 3 - would consistently hang and not start, until eventually timing out.

Given that we've rolled back the NUnit upgrade and will consider tackling that in a focussed PR just for that component.

The rest all looks good, and tests all pass.