More informative error messaging if time index is not increasing

### Parcels version

main

### Description

Provide more informative error messaging if the time index is not increasing (rather than the lower level time interval stuff).

cc @fluidnumerics-joe can you paste the reproducer here?

### Code sample

```python
# Paste your code within this block
```


```text
# Paste your error message within this block
```
