Optimize typeof(T).IsValueType

[EgorBo]

Fixes https://github.com/dotnet/coreclr/issues/23208
Also, contributes to https://github.com/dotnet/coreclr/issues/2591
Also, dotnet/aspnetcore@a42fff6

Replaces patterns like typeof(T).IsValueType or var.GetType().IsValueType() with constants (true/false).
E.g.:

class Case1
{
    public bool Foo<T>() => typeof(T).IsValueType;


    public bool Test1() => Foo<int>();
    public bool Test2() => Foo<string>();
}

Current codegen:

; Method Case1:Test1():bool:this
G_M15309_IG01:
       sub      rsp, 40
G_M15309_IG02:
       mov      rcx, 0xD1FFAB1E
       call     CORINFO_HELP_TYPEHANDLE_TO_RUNTIMETYPE
       mov      rcx, rax
       mov      rax, qword ptr [(reloc)]
       cmp      dword ptr [rcx], ecx
G_M15309_IG03:
       add      rsp, 40
       rex.jmp  rax
; Total bytes of code: 38


; Method Case1:Test2():bool:this
G_M7114_IG01:
       sub      rsp, 40
G_M7114_IG02:
       mov      rcx, 0xD1FFAB1E
       call     CORINFO_HELP_TYPEHANDLE_TO_RUNTIMETYPE
       mov      rcx, rax
       mov      rax, qword ptr [(reloc)]
       cmp      dword ptr [rcx], ecx
G_M7114_IG03:
       add      rsp, 40
       rex.jmp  rax
; Total bytes of code: 38

New codegen:

; Method Case1:Test1():bool:this
G_M15308_IG02:
       mov      eax, 1
G_M15308_IG03:
       ret      
; Total bytes of code: 6


; Method Case1:Test2():bool:this
G_M7113_IG02:
       xor      eax, eax
G_M7113_IG03:
       ret      
; Total bytes of code: 3

This PR also implements Type.IsPrimitive and Type.IsClass. Probably can implement more for free, e.g. Type.IsArray and Type.IsEnum (this one is virtual)

[EgorBo]

I find the following tests quite weird (matching current behaviour):

IsTrue (typeof(int*).IsClass)
IsTrue (typeof(Action<int>).IsClass);
IsFalse(typeof(ValueType).IsValueType);
IsTrue (typeof(ValueType).IsClass);

<removed>

[jkotas]

I find the following tests quite weird (matching current behaviour):

I believe that's because of the tests have a few copy&paste bugs.

[jkotas]

LGTM. Thank you!

I would like somebody from the JIT team to sign-off on this as well before merging.

[AndyAyersMS]

LGTM too. Thanks.