ENH: add to_xarray conversion method
supersedes #11950 
xref #10000 

using `xarray` >= 07.0

```
In [10]: Series([1,2,3]).to_xarray()
Out[10]: 
<xarray.DataArray (index: 3)>
array([1, 2, 3])
Coordinates:
  * index    (index) int64 0 1 2

In [11]: DataFrame({'A' : [1,2,3], 'B' : ['foo','bar','baz']}).to_xarray()
Out[11]: 
<xarray.Dataset>
Dimensions:  (index: 3)
Coordinates:
  * index    (index) int64 0 1 2
Data variables:
    A        (index) int64 1 2 3
    B        (index) object 'foo' 'bar' 'baz'

In [14]: Panel(np.random.randn(2, 3, 4)).to_xarray()
Out[14]: 
<xarray.DataArray (items: 2, major_axis: 3, minor_axis: 4)>
array([[[ 0.23726039,  0.44636322,  0.04425575,  1.06178388],
        [-0.58236405,  0.62602167,  0.36156612, -0.12687913],
        [-0.67854107,  0.72270844, -1.15402631, -1.89758909]],

       [[ 0.42948622,  0.93227075, -0.13943692,  0.83043343],
        [ 1.0355157 , -0.30532004, -0.16337369, -0.29283026],
        [ 0.65199775, -0.11131818,  0.37853134,  1.56620844]]])
Coordinates:
  * items       (items) int64 0 1
  * major_axis  (major_axis) int64 0 1 2
  * minor_axis  (minor_axis) int64 0 1 2 3
```

TODO:
- [ ] examples in doc-string
- [ ] how-to-convert/use xarray
