Add NEWS entries about JIT optimizations

and a related VM improvement.

JIT related commits:

* Code size reduction
  * Deduplicate functions on JIT compaction 818d6d3336
  * Avoid always inlining cold paths of ivar fcd2576290
  * Inline only fast path of rb_class_of b16a2aa938
  * Eliminate a call instruction on deopt 61b14bb32b
* Cold path partitioning
  * Mark method call slow paths as COLDFUNC 0e5a58b6bf
  * Mark vm_stackoverflow as NOINLINE COLDFUNC 9d71373c23
  * Create mjit_exec_slowpath and mark it as NOINLINE COLDFUNC 083a17a82a
* Primitive.attr! 'inline' / Integer#zero? 7561db8c00
  * Kernel#class 946e5cc668
  * (more to come...)
* Properly generate opt_send for cfunc cc 7982dc1dfd
* Optimize exivar access b736ea63bd
* Make JIT-ed leave leaf 151f8be40d
* Inline vm_call_cfunc b9d3ceee8f

VM:

* Enable fastpath on invokesuper 5c27681813
  * History: https://speakerdeck.com/k0kubun/ruby-3-samituto?slide=40 (in Japanese)

NEWS.md

@@ -235,6 +235,28 @@ Excluding feature bug fixes.
   a keyword splat to a method that accepts specific keywords
   does not allocate a hash.
 
+* `super` is optimized when the same type of method is called in the previous call,
+  when it's not refinements or an attr reader or writer.
+
+### JIT
+
+* Native functions shared by multiple methods are deduplicated on JIT compaction.
+
+* Decrease code size of hot paths by some optimizations and partitioning cold paths.
+
+* Not only pure Ruby methods but also some C methods skip pushing a method frame.
+
+  * `Kernel#class`, `Integer#zero?`
+
+* Always generate appropriate code for `==`, `nil?`, and `!` calls depending on
+  a receiver class.
+
+* Optimize instance variable access in some core classes like Hash and their subclasses
+
+* Eliminate VM register access on a method return
+
+* Optimize C method call a little
+
 ## Miscellaneous changes
 
 * Methods using `ruby2_keywords` will no longer keep empty keyword