set type of statement when processing GlobalRefs

Because we previously didn't set the type when processing `GlobalRef`,
the optimizer was inserting unnecessary `PiNode`s.

Before:

```julia
julia> x::Int = 1
1

julia> function f()
           global x = 0
           while x<10
               x += 1
           end
           x
       end
f (generic function with 1 method)

julia> @code_typed f()
CodeInfo(
1 ──       (Main.x = 0)::Any
2 ┄─ %2  = Main.x::Any
│    %3  = (isa)(%2, Int64)::Bool
└───       goto #4 if not %3
3 ── %5  = π (%2, Int64)
│    %6  = Base.slt_int(%5, 10)::Bool
└───       goto #5
4 ── %8  = (%2 < 10)::Bool
└───       goto #5
5 ┄─ %10 = φ (#3 => %6, #4 => %8)::Bool
└───       goto #10 if not %10
6 ── %12 = Main.x::Any
│    %13 = (isa)(%12, Int64)::Bool
└───       goto #8 if not %13
7 ── %15 = π (%12, Int64)
│    %16 = Base.add_int(%15, 1)::Int64
└───       goto #9
8 ── %18 = (%12 + 1)::Int64
└───       goto #9
9 ┄─ %20 = φ (#7 => %16, #8 => %18)::Int64
│          (Main.x = %20)::Any
└───       goto #2
10 ─ %23 = Main.x::Any
└───       return %23
) => Int64
```

This PR:

```julia
julia> @code_typed f()
CodeInfo(
1 ─      (Main.x = 0)::Any
2 ┄ %2 = Main.x::Int64
│   %3 = Base.slt_int(%2, 10)::Bool
└──      goto #4 if not %3
3 ─ %5 = Main.x::Int64
│   %6 = Base.add_int(%5, 1)::Int64
│        (Main.x = %6)::Any
└──      goto #2
4 ─ %9 = Main.x::Int64
└──      return %9
) => Int64
```

base/compiler/ssair/ir.jl

@@ -1001,6 +1001,10 @@ function process_node!(compact::IncrementalCompact, result_idx::Int, inst::Instr
         result[result_idx][:inst] = GotoNode(compact.bb_rename_succ[stmt.label])
         result_idx += 1
     elseif isa(stmt, GlobalRef) || isa(stmt, GotoNode)
+        result[result_idx][:inst] = stmt
+        result[result_idx][:type] = argextype(stmt, compact)
+        result_idx += 1
+    elseif isa(stmt, GotoNode)
         result[result_idx][:inst] = stmt
         result_idx += 1
     elseif isa(stmt, GotoIfNot) && compact.cfg_transforms_enabled

test/compiler/inline.jl

@@ -1069,3 +1069,18 @@ end
 @test fully_eliminated() do
     issue41694(2)
 end
+
+let m = Module()
+    @eval m begin
+        global x::Int = 0
+        function f()
+            global x = 0
+            while x<10
+                x += 1
+            end
+            x
+        end
+    end
+    src = code_typed1(f)
+    @test count(x -> isa(x, Core.PiNode), src.code) == 0
+end