dict docs: document that ordering of keys/values/pairs match iterate (#56842)

Fix #56841.

Currently the documentation states that keys(dict) and values(dict)
iterate in the same order. But it is not stated whether this is the same
order as that used by pairs(dict), or when looping, for (k,v) in dict.

This PR makes this guarantee explicit.

(cherry picked from commit 796d823)

Author: cossio

base/abstractdict.jl

@@ -86,8 +86,8 @@ Return an iterator over all keys in a dictionary.
 When the keys are stored internally in a hash table,
 as is the case for `Dict`,
 the order in which they are returned may vary.
-But `keys(a)` and `values(a)` both iterate `a` and
-return the elements in the same order.
+But `keys(a)`, `values(a)` and `pairs(a)` all iterate `a`
+and return the elements in the same order.
 
 # Examples
 ```jldoctest
@@ -112,8 +112,8 @@ Return an iterator over all values in a collection.
 When the values are stored internally in a hash table,
 as is the case for `Dict`,
 the order in which they are returned may vary.
-But `keys(a)` and `values(a)` both iterate `a` and
-return the elements in the same order.
+But `keys(a)`, `values(a)` and `pairs(a)` all iterate `a`
+and return the elements in the same order.
 
 # Examples
 ```jldoctest
@@ -136,6 +136,10 @@ values(a::AbstractDict) = ValueIterator(a)
 Return an iterator over `key => value` pairs for any
 collection that maps a set of keys to a set of values.
 This includes arrays, where the keys are the array indices.
+When the entries are stored internally in a hash table,
+as is the case for `Dict`, the order in which they are returned may vary.
+But `keys(a)`, `values(a)` and `pairs(a)` all iterate `a`
+and return the elements in the same order.
 
 # Examples
 ```jldoctest

test/dict.jl

@@ -763,6 +763,13 @@ end
           [v for (k, v) in d] == [d[x[1]] for (i, x) in enumerate(d)]
 end
 
+@testset "consistency of dict iteration order (issue #56841)" begin
+    dict = Dict(randn() => randn() for _ = 1:100)
+    @test all(zip(dict, keys(dict), values(dict), pairs(dict))) do (d, k, v, p)
+        d == p && first(d) == first(p) == k && last(d) == last(p) == v
+    end
+end
+
 @testset "generators, similar" begin
     d = Dict(:a=>"a")
     # TODO: restore when 0.7 deprecation is removed