fix: global project_tld should default to 'ddev.site', not empty, fixes #4290

[rfay]

The Issue

• Use the default project_tld ddev.site instead of "" in the global_config.yaml #4290

@rpkoller pointed out that the global_config.yaml would be more useful if it just specified ddev.site as the project_tld.

How This PR Solves The Issue

Make it explicit in the config.

Manual Testing Instructions

• Test to make sure changing global project_tld still works fine
• Test to make sure default config with ddev.site works fine. Automated tests ought to do this just fine.

[github-actions]

Download the artifacts for this pull request:

• all-ddev-executables.zip
• ddev-macos-amd64.zip
• ddev-macos-arm64.zip
• ddev-linux-arm64.zip
• ddev-linux-amd64.zip
• ddev-windows-amd64-installer.zip

See Testing a PR

[stasadev]

Noticed a bug, it's not even related to the changes made in this PR (reproducible on the stable DDEV), but it probably fits here:

When you set the global TLD to test and the project TLD to ddev.site, the project config is not set, it seems that there is some hardcode in the code for nodeps.DdevDefaultTLD:

ddev config global --project-tld test
ddev config --project-tld ddev.site

On the other hand, this override works if I set it manually: project_tld: ddev.site in .ddev/config.yaml. But it is lost when I run ddev config --auto or ddev config --project-tld ddev.site.

[rfay]

OK with me for you to fix that here.

[stasadev]

I made a change in the app.WriteConfig(), will see how the tests go.

[stasadev]

It should be fine, I tested it again and didn't find any flaws.