Unwind just the "pseudorandom probing" part of recent sets,tables changes (#13816)

* Unwind just the "pseudorandom probing" (whole hash-code-keyed variable
stride double hashing) part of recent sets & tables changes (which has
still been causing bugs over a month later (e.g., two days ago
https://github.com/nim-lang/Nim/issues/13794) as well as still having
several "figure this out" implementation question comments in them (see
just diffs of this PR).

This topic has been discussed in many places:
  https://github.com/nim-lang/Nim/issues/13393
  https://github.com/nim-lang/Nim/pull/13418
  https://github.com/nim-lang/Nim/pull/13440
  https://github.com/nim-lang/Nim/issues/13794

Alternative/non-mandatory stronger integer hashes (or vice-versa opt-in
identity hashes) are a better solution that is more general (no illusion
of one hard-coded sequence solving all problems) while retaining the
virtues of linear probing such as cache obliviousness and age-less tables
under delete-heavy workloads (still untested after a month of this change).

The only real solution for truly adversarial keys is a hash keyed off of
data unobservable to attackers.  That all fits better with a few families
of user-pluggable/define-switchable hashes which can be provided in a
separate PR more about `hashes.nim`.

This PR carefully preserves the better (but still hard coded!) probing
of the  `intsets` and other recent fixes like `move` annotations, hash
order invariant tests, `intsets.missingOrExcl` fixing, and the move of
`rightSize` into `hashcommon.nim`.

* Fix `data.len` -> `dataLen` problem.

lib/pure/collections/sets.nim

@@ -68,7 +68,6 @@ type
     ## before calling other procs on it.
     data: KeyValuePairSeq[A]
     counter: int
-    countDeleted: int
 
 type
   OrderedKeyValuePair[A] = tuple[
@@ -81,7 +80,6 @@ type
     ## <#initOrderedSet,int>`_ before calling other procs on it.
     data: OrderedKeyValuePairSeq[A]
     counter, first, last: int
-    countDeleted: int
 
 const
   defaultInitialSize* = 64
@@ -249,7 +247,7 @@ iterator items*[A](s: HashSet[A]): A =
   ##   echo b
   ##   # --> {(a: 1, b: 3), (a: 0, b: 4)}
   for h in 0 .. high(s.data):
-    if isFilledAndValid(s.data[h].hcode): yield s.data[h].key
+    if isFilled(s.data[h].hcode): yield s.data[h].key
 
 proc containsOrIncl*[A](s: var HashSet[A], key: A): bool =
   ## Includes `key` in the set `s` and tells if `key` was already in `s`.
@@ -341,7 +339,7 @@ proc pop*[A](s: var HashSet[A]): A =
     doAssertRaises(KeyError, echo s.pop)
 
   for h in 0 .. high(s.data):
-    if isFilledAndValid(s.data[h].hcode):
+    if isFilled(s.data[h].hcode):
       result = s.data[h].key
       excl(s, result)
       return result
@@ -574,8 +572,7 @@ proc map*[A, B](data: HashSet[A], op: proc (x: A): B {.closure.}): HashSet[B] =
 proc hash*[A](s: HashSet[A]): Hash =
   ## Hashing of HashSet.
   for h in 0 .. high(s.data):
-    if isFilledAndValid(s.data[h].hcode):
-      result = result xor s.data[h].hcode
+    result = result xor s.data[h].hcode
   result = !$result
 
 proc `$`*[A](s: HashSet[A]): string =
@@ -593,6 +590,7 @@ proc `$`*[A](s: HashSet[A]): string =
   ##   # --> {no, esc'aping, is " provided}
   dollarImpl()
 
+
 proc initSet*[A](initialSize = defaultInitialSize): HashSet[A] {.deprecated:
      "Deprecated since v0.20, use 'initHashSet'".} = initHashSet[A](initialSize)
 
@@ -624,7 +622,7 @@ template forAllOrderedPairs(yieldStmt: untyped) {.dirty.} =
     var idx = 0
     while h >= 0:
       var nxt = s.data[h].next
-      if isFilledAndValid(s.data[h].hcode):
+      if isFilled(s.data[h].hcode):
         yieldStmt
         inc(idx)
       h = nxt
@@ -858,7 +856,7 @@ proc `==`*[A](s, t: OrderedSet[A]): bool =
   while h >= 0 and g >= 0:
     var nxh = s.data[h].next
     var nxg = t.data[g].next
-    if isFilledAndValid(s.data[h].hcode) and isFilledAndValid(t.data[g].hcode):
+    if isFilled(s.data[h].hcode) and isFilled(t.data[g].hcode):
       if s.data[h].key == t.data[g].key:
         inc compared
       else: