Add hashable/immutable variant for `DisjointSet` objects

[maxale]

Problem Description

Currently it impossible to use DisjointSet objects as keys due to the lack of hashability. For example, hash(DisjointSet(5)) gives an error TypeError: unhashable type: 'sage.sets.disjoint_set.DisjointSet_of_integers'

Proposed Solution

Add immutability option for DisjointSet objects (say, like the one in graphs).

Alternatives Considered

Alternatively, a reasonable option is to convert to a SetPartition object, which is hashable. However, the reverse conversion is currently broken - see #38415

Additional Information

No response

Is there an existing issue for this?

• [X] I have searched the existing issues for a bug report that matches the one I want to file, without success.

[Deepakchowdavarapu]

I can work on this Issue , please Assign it to me