[dart2js] New rti tracking issue

[rakudrama]

This is a general tracking issue for new rti implementation tasks.

Testing:

• Run modular and some unit tests with new-rti

Correctness:

• Full function type parsing and subtyping
• Full generic function type parsing
• Full generic function type subtyping
• Full generic function type toString()
• Pass new rti for element type to generator bodies
• Access new rti in forwarding stubs
• Generic function instantiation - creating and calling
• Generic function instantiation - closure type and subtyping
• Reify erased type variables correctly

Basic performance:

• Lower is-tests for simple types
• Lower as-checks for simple types
• Group multiple type parameters into tuples ([dart2js] Pass type arguments as tuples or useful interface type #47484)
• Consistent ordering of environment accesses (becomes trivial when parameters grouped)
• Reduction of class type variables (UnmodifableListBase.E --> ListMixin.E)
  • Not worth implementing; see https://dart-review.googlesource.com/c/sdk/+/120745
• Closure type lookup
  • Accelerate lookup of closure type by installing property
  • Remove closure classes from supertypes data
• Lower H._instanceType(x) to x.$ti in more cases

Other optimizations:

• Make more classes have their type available through .$ti. Getter for $ti on Object, Closure, BoundClosure, StaticClosure. Object uses dynamic constructor's name, Closure could use cached version. THIS SEEMS TO BE VERY DIFFICULT. Defining a getter for Object.prototype.$ti seems to prevent using $ti as a normal property in subclasses. We could work around this by using a different name, but that throws out what we are looking for - a single megamorphic dispatch to most types. The 'different name' is just alternate syntax for H._instanceType(x).
• Is there some more direct way to cache the constructor name version?
• Reduce $ti._eval$1("1") --> $ti._rest[0]
• Reduce $ti._rest[0] --> $ti._precomputed1.
• Use instanceof
  The current general-is-test works (and fails) until instances of the class are created, which implies that the constructor is loaded.
  • Install instanceof predicates on Rti objects for types where instanceof works, and type flows to is-check. This should be done in the deferred unit that declares the class constructor. findType("Foo")._is=function(o){return o instanceof X.Foo}
  • Generate instanceof directly like for old Rti. This would be restricted to code where the constructor is available, e.g. the class constructor is in the same deferred unit as the usage (in old Rti this is OK because the class constructor is the type).
• x as T --> x under branch where x is T is true. Old rti does this, relying on GVN of x and T,

Cleanup:

• Remove recognizing "dynamic" as a recipe, use only @.
• Remove encodeRecipeWithVariablesReplaceByAny
• remove _Type.==, remove the workaround in kernel_impact.dart#L876 and update CFE missing compile time error: const keys/switch cases should not implement == #32557

JS interop fix:

• Cleanup JSArray<dynamic> --> JSArray<any>.