[torque] Fix crash when calling builtin via function pointer

When calling a builtin via a function pointer, torque tries to find any
builtin with the same parameter types for a descriptor. If no such
builtin exist, we currently crash.

Example:

type DoesNotExistFn = builtin(Context, Smi, Smi, Smi) => Smi;
macro TestMacro(c: Context, fn: DoesNotExistFn) {
  let result: Smi = fn(c, 1, 2, 3);
}

R=tebbi@chromium.org

Bug: v8:7793
Change-Id: Ia7436dc6541aca5de2e8dcb6b2a09978a1af9d39
Reviewed-on: https://chromium-review.googlesource.com/1123821
Reviewed-by: Tobias Tebbi <tebbi@chromium.org>
Commit-Queue: Simon Zünd <szuend@google.com>
Cr-Commit-Position: refs/heads/master@{#54165}

src/torque/implementation-visitor.cc

@@ -1428,6 +1428,11 @@ VisitResult ImplementationVisitor::GeneratePointerCall(
 
   Builtin* example_builtin =
       declarations()->FindSomeInternalBuiltinWithType(type);
+  if (!example_builtin) {
+    std::stringstream stream;
+    stream << "unable to find any builtin with type \"" << *type << "\"";
+    ReportError(stream.str());
+  }
 
   if (is_tailcall) {
     source_out() << "TailCallStub(";