GH-118095: Use _DYNAMIC_EXIT to stitch traces ending in unbalanced returns or yields.

[markshannon]

We stop a lot of traces at yields and returns. This PR adds a _DYNAMIC_EXIT uop at the end of those traces.

Stats and JIT performance

Instructions in billions

Instructions	Main	This PR
Tier 1	97.1	71.2
Tier 2	196.0	243.8

• Issue: Increase the number of micro-ops that we can handle in tier 2 #118095

[brandtbucher]

What do you attribute the slowdown to? The inefficiency of _DYNAMIC_EXIT?

[markshannon]

What do you attribute the slowdown to? The inefficiency of _DYNAMIC_EXIT?

I don't know. Maybe its _DYNAMIC_EXIT, maybe we are compiling more instructions that don't compile very well, maybe something else entirely.
There is no obvious pattern to the slowdown, so it might be noise or it might be some diffuse effect like cache misses. 🤷‍♂️