Various bug fixes and improvements from dsharletg/sliding-window

[dsharletg]

• Fix cloning a semaphore more than once.
• Ignore promise_clamped in solve
• Acquire is not a no-op, even if it's empty
• Handle nested vectors in bounds_of_lanes

By @abadams:

• Don't count unlikely loops as inner loops for likely_if_innermost
• Handle LE/LT in bounds_of_lanes

[dsharletg]

Review ping on this, this is a subset of the changes from #5755, in an attempt to make that PR smaller and more focused. @abadams