Review and update `ryujit-tutorial.md`

While still largely accurate, the document contains some bits of outdated information, e. g.:

.NET is somewhat unique in that it currently has a single-tier JIT – no interpreter, and no re-optimizing JIT.
While an interpreter exists, and experimentation has been done on re-jitting, the current model remains single-tier.

And old-style dumps:

▌  Statement  (top level) (IL 0x01D
│        ┌──▌  const int 1
│     ┌──▌  & int
│     │  └──▌  lclVar int V08
│  ┌──▌  + int
│  │  └──▌  lclVar int V06
└──▌  = int
   └──▌  lclVar int V06

The accompanying ryu-jit-overview.md document should also be reviewed and updated.

category:documentation theme:big-bets