Fix Issue 24823 - std.json: Allow optionally preserving the order of fields in JSON objects

[CyberShadow]

This is the same goal as #6059 , but a more minimal / conservative approach - instead of adding a policy framework, this is behind a new JSONOptions flag.

In theory this is perfectly backwards compatible, as pre-existing D code will never cause any orderedObject to be created. The orderedObject type is entirely opt-in, whether via JSONOptions.preserveObjectOrder, or created manually by starting from a JSONValue.emptyOrderedObject or the .orderedObject setter.

The only gotcha might be any possible final switch-es over JSONType, let's see what BuildKite says - if this is an issue then JSONType.orderedObject could be moved to a bool instead.

[dlang-bot]

Thanks for your pull request, @CyberShadow!

Bugzilla references

Auto-close	Bugzilla	Severity	Description
✓	24823	enhancement	std.json: Allow optionally preserving the order of fields in JSON objects

Testing this PR locally

If you don't have a local development environment setup, you can use Digger to test this PR:

dub run digger -- build "master + phobos#9064"

[CyberShadow]

The only gotcha might be any possible final switch-es over JSONType, let's see what BuildKite says - if this is an issue then JSONType.orderedObject could be moved to a bool instead.

Indeed this was an issue, and, done.