add vm_allocate for apple

[hjmallon]

We have vm_deallocate, why not vm_allocate too?

I am not totally sure whether these should live here or in mach2?

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[JohnTitor]

If it's related to mach items it should live in mach2, but indeed it's weird that we don't have allocate while we do deallocate, so @bors r+

[bors]

📌 Commit d0d0db2 has been approved by JohnTitor

It is now in the queue for this repository.

[bors]

⌛ Testing commit d0d0db2 with merge 4ac74f5...

[bors]

☀️ Test successful - checks-actions, checks-cirrus-freebsd-12, checks-cirrus-freebsd-13, checks-cirrus-freebsd-14
Approved by: JohnTitor
Pushing 4ac74f5 to main...