Make sleep work with isolation enabled

[pvdrz]

Implement a virtual monotone clock that can be used to track time while isolation is enabled. This virtual clock keeps an internal nanoseconds counter that will be increased by a fixed amount at the end of every basic block.

When a process sleeps, this clock will return immediately and increase the counter by the interval the process was supposed to sleep. Making miri execution faster than native code .

cc @RalfJung @saethlin @JakobDegen

[bors]

☔ The latest upstream changes (presumably #2363) made this pull request unmergeable. Please resolve the merge conflicts.

[bors]

☔ The latest upstream changes (presumably #2524) made this pull request unmergeable. Please resolve the merge conflicts.

[RalfJung]

I did some tweaking to the API to make it match the one from the standard library more closely, which overall makes this a much smaller conceptual change for the rest of Miri. Please take a look and let me know what you think. :)

If you like it, please squash the commits together a little -- this is ready to go, as far as I am concerned.

[saethlin]

I just have nits. This is a much smaller and more maintainable change than I somehow expected!

[saethlin]

👍 Squash the commits down some then I'll approve this. (also if you want a nice description of this to live in the commit history you could write a PR description)

[saethlin]

@bors r+

[bors]

📌 Commit c834637 has been approved by saethlin

It is now in the queue for this repository.

[bors]

⌛ Testing commit c834637 with merge 2f1fa12...

addressed

[bors]

☀️ Test successful - checks-actions
Approved by: saethlin
Pushing 2f1fa12 to master...