[Mapping] Implementing == and != operators

[roigcarlo]

📝 Description
== and != operators are needed for the GTest

currently the tests assume that distance is not checked, but it should?

🆕 Changelog

• Added == operator
• Added != operator
• Modify the tests accordingly

[roigcarlo]

@loumalouomega I am not sure if we can approve this right away, the idea was to discuss with @philbucher if the equality operators need to take into consideration the distance or not.

[philbucher]

I am aware, will check in on the weekend. This is sth I need to think about and remember what I did
Otherwise it will break the braycentric mapper

[roigcarlo]

Any news?

[philbucher]

Now I remember!
The id does not matter for the comparison, I only care about the distance
I.e. the inheritance from IndexedObject does not matter here

[philbucher]

wait, I think there is more to it after all 🤔

[roigcarlo]

@philbucher Done with the changes.