Improve apt packages and docs, fixes #4112, fixes #4113, fixes #4125

[rfay]

The Problem/Issue/Bug:

• Unable to locate package certutil error after running sudo apt-get update && sudo apt-get install -y certutil xdg-utils - step 14 of ddev wsl2 install #4112
• Why are WSL2 and Linux tab ddev install steps different when they both say to install inside distro? #4113
• apt installation doesn't properly install bash completions #4125

How this PR Solves The Problem:

Manual Testing Instructions:

Automated Testing Overview:

Related Issue Link(s):

Release/Deployment notes:

[rfay]

@bserem I'd love it if you can review this and also test out the package. You can get it by temporarily

1. sudo apt remove ddev
2. Put deb [trusted=yes] https://apt.fury.io/rfay-test-org/ / in your /etc/apt/sources.list.d/ddev.list

This will get a test version pushed up from my fork, v1.20.1-alpha2. You can uninstall and go back to regular settings afterward.

[bserem]

@rfay thanks for working on this.

I can verify that it works on my machine. So, that's one off the list!

Update: removing and installing the previous version also removed bash completion, so uninstallation also works properly

[rfay]

Thanks for testing and for checking this through so carefully. Not sure why I thought it would work as is. Probably because homebrew takes care of those things a bit magically.

[bserem]

Anytime!

Apt is a new territory for ddev, things will be ironed out eventually. Personally I'm grateful for the new repo, it makes more sense for Linux systems.

See ya on the next issue