DEPR: Tick comparison with str
ATM Tick offset comparisons try casting strings to offsets with to_offset before doing == or !=, but not for inequalities:

```
>>> m = pd.offsets.Minute(4)
>>> m == "4min"
True
>>> m < "5min"
TypeError: Invalid comparison between Minute and str
```

In order to make this behavior more consistent, we should deprecate allowing str casting for == and !=.  This would allow us to dispatch to the Timedelta inequalities, which have better handling for corner cases anyway (e.g. `m < np.ndarray([m, m]` which Timedelta gets right but Tick messes up)