Revert "core.thread refactor: osthread module"

[Geod24]

Reverts #2689

Because it apparently broke DMD test suite.

[dlang-bot]

Thanks for your pull request, @Geod24!

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Testing this PR locally

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[Geod24]

CC @thewilsonator @baziotis

[Geod24]

@thewilsonator : Can we merge this ?

[rainers]

A bit too late, but #2801 should fix the issue, too.

[thewilsonator]

Thanks, but even if it does we, should enable the azure pipelines for druntime to test it anyway.

[baziotis]

A bit too late, but #2801 should fix the issue, too.

TBH, I didn't have the time to look thoroughly what the problem was, but #2689 did not change any code. I see that yours does a small change. Which makes me think about how the problem arose in the first place and why it didn't happen with the previous.

[thewilsonator]

Possibly slack layout, it should be pretty simple to revert this once the azure pipelines are set up for druntime.

[thewilsonator]

@baziotis Azure pipelines are now set up, could you please reopen another PR. it seems that this can't be simply reverted due to merge conflicts.

[baziotis]

Good! Yes, I assume tomorrow I will have time.