Infer ExtensionDtype based on object
Would it be possible to infer ExtensionDtypes based on the objects inside a list/array that are used to construct a series?

Eg with an array of pint's Quantity objects:
```python3
>>> array_of_qty
array([<Quantity(67.0, 'meter')>, <Quantity(61.0, 'meter')>,
       <Quantity(30.0, 'meter')>, ..., <Quantity(293.0, 'meter')>,
       <Quantity(886.0, 'meter')>, <Quantity(165.0, 'meter')>],
      dtype=object)
```
Could pandas infer the dtype as PintType in this command?:
```python3
df.elevation = array_of_qty
```