remove a condition that table size must be passed as power of 2 (#14926)

* remove a condition that table size must be passed as power of 2
* remove power-of-2 condition from sets and sharedtables
* remove power-of-2 condition from deques
* use 'correctSize' for both branches
* prettify changelog.md and fix typos
* add a changelog entry
* fix double-call of 'right-size'
* fix the same thing in sets.nim
* introduce a new internal proc `slotsNeeded`

Deprecate the public proc `rightSize`, which is not needed anymore.
Now it is an identity function, allowing the old code to work
correctly and without extra allocations.

lib/pure/collections/setimpl.nim

@@ -16,12 +16,12 @@ template dataLen(t): untyped = len(t.data)
 include hashcommon
 
 template initImpl(s: typed, size: int) =
-  assert isPowerOfTwo(size)
+  let correctSize = slotsNeeded(size)
   when s is OrderedSet:
     s.first = -1
     s.last = -1
   s.counter = 0
-  newSeq(s.data, size)
+  newSeq(s.data, correctSize)
 
 template rawInsertImpl() {.dirty.} =
   if data.len == 0: