move assertions and iterators out of system.nim (#10597)

* move assertions and iterators out of system.nim
* limit nimsuggest tests to the first 3 suggestions

lib/system/fatal.nim

@@ -0,0 +1,47 @@
+{.push profiler: off.}
+when hostOS == "standalone":
+  include "$projectpath/panicoverride"
+
+  proc sysFatal(exceptn: typedesc, message: string) {.inline.} =
+    panic(message)
+
+  proc sysFatal(exceptn: typedesc, message, arg: string) {.inline.} =
+    rawoutput(message)
+    panic(arg)
+
+elif defined(nimQuirky) and not defined(nimscript):
+  proc name(t: typedesc): string {.magic: "TypeTrait".}
+
+  proc sysFatal(exceptn: typedesc, message, arg: string) {.inline, noReturn.} =
+    var buf = newStringOfCap(200)
+    add(buf, "Error: unhandled exception: ")
+    add(buf, message)
+    add(buf, arg)
+    add(buf, " [")
+    add(buf, name exceptn)
+    add(buf, "]")
+    cstderr.rawWrite buf
+    quit 1
+
+  proc sysFatal(exceptn: typedesc, message: string) {.inline, noReturn.} =
+    sysFatal(exceptn, message, "")
+
+else:
+  proc sysFatal(exceptn: typedesc, message: string) {.inline, noReturn.} =
+    when declared(owned):
+      var e: owned(ref exceptn)
+    else:
+      var e: ref exceptn
+    new(e)
+    e.msg = message
+    raise e
+
+  proc sysFatal(exceptn: typedesc, message, arg: string) {.inline, noReturn.} =
+    when declared(owned):
+      var e: owned(ref exceptn)
+    else:
+      var e: ref exceptn
+    new(e)
+    e.msg = message & arg
+    raise e
+{.pop.}