some test cleanups & category reorganization (#22010)

* clean up some test categories

* mention exact slice issue

* magics into system

* move trangechecks into overflow

* move tmemory to system

* try fix CI

* try fix CI

* final CI fix

tests/overflow/trangechecks.nim

@@ -0,0 +1,48 @@
+discard """
+  output: '''10
+10
+1
+1
+true'''
+"""
+
+# bug #1344
+
+var expected: int
+var x: range[1..10] = 10
+
+try:
+  x += 1
+  echo x
+except OverflowDefect, RangeDefect:
+  expected += 1
+  echo x
+
+try:
+  inc x
+  echo x
+except OverflowDefect, RangeDefect:
+  expected += 1
+  echo x
+
+x = 1
+try:
+  x -= 1
+  echo x
+except OverflowDefect, RangeDefect:
+  expected += 1
+  echo x
+
+try:
+  dec x
+  echo x
+except OverflowDefect, RangeDefect:
+  expected += 1
+  echo x
+
+echo expected == 4
+
+# bug #13698
+var
+  x45 = "hello".cstring
+  p = x45.len.int32