Invalidate icache on stub/var import update

Because this needs to be done within a syscall, uses `blocks.InvalidateICache()`.  Took me a while to realize why that was glitching out at first, but I figured it out.

I hope I didn't make `JitBlockCache::GetBlockNumberFromEmuHackOp()` noticeably slower (I don't think so.)

Also worth noting is that `JitBlockCache::InvalidateICache()` probably won't work if continuing is enabled.  I think we'd need to keep two maps to make that work (one for start, one for end)?

We could probably also now implement sceKernelInvalidateICache and friends now, although didn't want to do that in this pull.

-[Unknown]