Add osrpoint opcode for hot loop detection.
Trigger OSR; just stub the procedure for now.
Start sketching out OSR handling.
Add sp_osrfinalize spesh op.

Used to handle logging runs through the loop, and will trigger the
final optimization afterwards.
Convey "are we doing OSR" deeper into spesh.
Handle osrpoint in spesh logging setup.

If we are doing OSR, turn it into sp_osrfinalize; otherwise, toss it.
First pass at making OSR work.

Handles the basic cases, though doesn't always work out yet, and does
not yet handle the inlining case.
Delete sp_osrfinalize in final optimization phase.
Use dedicated OSR deopt mark and annotation.

Makes it easier to understand what's going on, and provides better
control over motion when we delete the osrpoint.
Can't cache OSR index in multi-osrpoint frame.
Handle OSR and inlining interaction.
Enable inlining and OSR to be disabled.

Means we can evaluate their effect, as well as isolate bugs more
easily.
Correct off-by-one OSR logging run issue.