Removed the D module due to lack of support

[samsinsane]

What does this PR do?

Removes the D module.

How does this PR change Premake's behavior?

No more support for the D language.

Anything else we should know?

This module has blocked the removal of the gmake module for the last 7 years. I was one of the people voting to keep the module, but having looked at the timelines, I have re-evaluated my opinion.

I decided to remove the entire module instead of just the gmake support because this module hasn't received any real changes since 2018, except for once in 2021 (#1658) and once in 2019 (#1298). All other changes were instances of a feature or new value being added to all of the modules in one go, so it's unclear if these changes were correct/compatible or not. This module was only added into core in 2015, which means it has been unsupported for longer than it was supported.

Did you check all the boxes?

• [x] Focus on a single fix or feature; remove any unrelated formatting or code changes
• [ ] Add unit tests showing fix or feature works; all tests pass
• [ ] Mention any related issues (put closes #XXXX in comment to auto-close issue when PR is merged)
• [x] Follow our coding conventions
• [x] Minimize the number of commits
• [x] Align documentation to your changes

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[tritao]

Sad to see it go as D is actually a pretty cool language, but if does not have any support seems like the way to go.

[nickclark2016]

At some point it may be worth pulling this into a module, but as I don't use D and have just helped to maintain it from a very high level, I do agree with it's removal from core.