Ensure invalidated target gets logged (JuliaLang#49048)

To interpret causes of invalidation, it's helpful to understand what
signature got invalidated. JuliaLang#48954 inadvertently dropped this info
from the logging stream; this commit restores it.

src/gf.c

@@ -2021,6 +2021,11 @@ JL_DLLEXPORT void jl_method_table_insert(jl_methtable_t *mt, jl_method_t *method
                         }
                         jl_array_ptr_1d_push(oldmi, (jl_value_t*)mi);
                         invalidate_external(mi, max_world);
+                        if (_jl_debug_method_invalidation) {
+                            jl_array_ptr_1d_push(_jl_debug_method_invalidation, (jl_value_t*)mi);
+                            loctag = jl_cstr_to_string("jl_method_table_insert");
+                            jl_array_ptr_1d_push(_jl_debug_method_invalidation, loctag);
+                        }
                     }
                 }
             }

test/worlds.jl

@@ -408,3 +408,27 @@ wc_aiw2 = get_world_counter()
 @test Base.invoke_in_world(wc_aiw2, f_inworld, 2) == "world two; x=2"
 @test Base.invoke_in_world(wc_aiw1, g_inworld, 2, y=3) == "world one; x=2, y=3"
 @test Base.invoke_in_world(wc_aiw2, g_inworld, 2, y=3) == "world two; x=2, y=3"
+
+# logging
+mc48954(x, y) = false
+mc48954(x::Int, y::Int) = x == y
+mc48954(x::Symbol, y::Symbol) = x == y
+function mcc48954(container, y)
+    x = container[1]
+    return mc48954(x, y)
+end
+
+mcc48954(Any[1], 1)
+mc48954i = method_instance(mc48954, (Any, Int))
+mcc48954i = method_instance(mcc48954, (Vector{Any}, Int))
+list48954 = ccall(:jl_debug_method_invalidation, Any, (Cint,), 1)
+mc48954(x::AbstractFloat, y::Int) = x == y
+ccall(:jl_debug_method_invalidation, Any, (Cint,), 0)
+@test list48954 == [
+    mcc48954i,
+    1,
+    mc48954i,
+    "jl_method_table_insert",
+    which(mc48954, (AbstractFloat, Int)),
+    "jl_method_table_insert"
+]