KSP2 Performance Issues

(Filing at the request of the JB folks for referencing)

I re-profiled our builds with KSP2 with 2.0.21-1.0.27. Unfortunately, across the board in a bunch of benchmarks I found that
- abi change - KSP2 is ~40-50% slower
- noabi change - KSP2 is 80-100% slower
- clean build - negligible/amortized by the clean build
-
If I just benchmark expensive our two most expensive KSP tasks with `, KSP2 is around 20-30% slower.

Other notes:
- We give the kotlin and gradle daemons the same memory, and these benchmarks were run on overpowered AWS boxes
- None of these builds were experiencing memory pressure with the settings they had (somewhere in the dozens of GB for xmx)

time-to-task-start is more or less the same, assumes a hot configuration cache

Here's a few samples. Looking again there is some GC time creeping into some of these that I'll look closer into, but not enough to majorly skew the larger trend