Fix bad c-tor for WeakKeyDict. Fix #35782 (#35783)

(cherry picked from commit ba91a98)

Author: kshyatt

base/weakkeydict.jl

@@ -69,6 +69,7 @@ function WeakKeyDict(kv)
     end
 end
 
+sizehint!(d::WeakKeyDict, newsz) = sizehint!(d.ht, newsz)
 empty(d::WeakKeyDict, ::Type{K}, ::Type{V}) where {K, V} = WeakKeyDict{K, V}()
 
 islocked(wkh::WeakKeyDict) = islocked(wkh.lock)

test/dict.jl

@@ -841,6 +841,7 @@ Dict(1 => rand(2,3), 'c' => "asdf") # just make sure this does not trigger a dep
     @test isa(WeakKeyDict(A=>2, B=>3, C=>4), WeakKeyDict{Array{Int,1},Int})
     @test WeakKeyDict(a=>i+1 for (i,a) in enumerate([A,B,C]) ) == wkd
     @test WeakKeyDict([(A,2), (B,3), (C,4)]) == wkd
+    @test WeakKeyDict{typeof(A), Int64}(Pair(A,2), Pair(B,3), Pair(C,4)) == wkd
     @test WeakKeyDict(Pair(A,2), Pair(B,3), Pair(C,4)) == wkd
     @test isa(WeakKeyDict(Pair(A,2), Pair(B,3.0), Pair(C,4)), WeakKeyDict{Array{Int,1},Any})
     @test isa(WeakKeyDict(Pair(convert(Vector{Number}, A),2), Pair(B,3), Pair(C,4)), WeakKeyDict{Any,Int})