Fix deprecation of DisjointSets(xs...) to avoid warning on package load

[odow]

This deprecation broke JuMP and a bunch of related packages that test with --depwarn=error (to avoid using deprecated bindings): jump-dev/JuMP.jl#4058

One downside to this PR is that it introduces a new (deprecated) DisjointSet(xs...) method.

There is already a test that DisjointSets(xs...) is equivalent to DisjointSet(xs...) and then DisjointSet(xs):

DataStructures.jl/test/test_disjoint_set.jl

Line 168 in bf5146d

@test DisjointSets(1:10...) == DisjointSet(1:10)

[oxinabox]

Thank you.
Looks good.
Can you bump the version number?

[odow]

I bumped but then reverted. There's actually a few commits on master, so I'll make a separate PR that updates the version and adds release notes.