DEPR: remove Int|Uint|Float64Index from conftest & _testing
Progress towards #42717.

In particular cleans up conftest.py::indices_dict to not use old style indexes and cleans up the `tm.make*Index` functions to not return old style numeric indexes.

I've kept `tm.MakeIntIndex`etc. and just made them tighter versions of `tm.makeNumericIndex` though if they should be deleted that is also fine for me.
Thanks @topper-123 