Implement equals and hashCode in Chunk class

[jpraet]

See #4296. There is a problem with the PR #4300 that made it into 5.0.1:
it adds equals and hashCode to the ChunkIterator class instead of to the Chunk class.

[fmbenhassine]

Thank you for raising this! The PR was off-by-one brace and I missed that when reviewing it. My bad 🤦..

I will fix this in 5.0.2.

[baezzys]

Sorry for my mistake.. I'll fix it.

[fmbenhassine]

This was resolved with #4317, but has exposed a seemingly old hidden bug as explained here: #4317 (comment).

I created #4370 for that.