ENH: allow object-dtype Index to do arithmetic ops
Implement ops in the base Index class to work the same as Series versions.
I seem to remember an issue about this (which this PR would close), but can't directly find it.

This needs some more tests?

There are also some definitions of arithmetic ops that might no longer be needed?

https://github.com/pandas-dev/pandas/blob/c0ff67a22df9c18da1172766e313732ed2ab6c30/pandas/core/indexes/base.py#L2331-L2354 Can you give some context for closing? clearing the queue until I can address the comments properly