Deprecate Log4jTextFormatter and Log4netTextFormatter

[0xced]

Description

Recommend using Serilog.Formatting.Log4Net instead.

Serilog.Formatting.Log4Net is better that the provided Log4jTextFormatter and Log4netTextFormatter classes as it is configurable and well documented.

Disclaimer: I am the author of Serilog.Formatting.Log4Net. 😉

Checklist

• [x] My code follows the style guidelines of this project
• [x] I have performed a self-review of my own code
• [x] I have commented my code, particularly in hard-to-understand areas
• [x] I have made corresponding changes to the documentation
• [x] I have added tests that prove my fix is effective or that my feature works

[FantasticFiasco]

Hi @0xced!

I've given this some thought, weighting pros and cons. On the positive side it means that I can delete code, that I don't have to manage it anymore. That is great! On the negative side I lose control and introduce risk. Looking at the changes in the specific files, there hasn't been any for a really long time. That diminishes the value of this change. Also, dependencies comes at a cost. For a user this means taking a dependency not on one NuGet package but instead two. And although Dependabot and Renovate are fantastic tools for dependency management, I must believe that many companies host their source on-prem, where these tools cannot run. As a user there's also is the fear on the compatibility matrix between the two tools.

Let's leave this PR open, but I won't merge it until I get more feedback or encounter a problem with my implementation that would be solved by your implementation. I wish you all the best of luck in your open source endeavour!