feat: add method wrapper for xr.align

[coroa]

Changes proposed in this Pull Request

Adds a wrapper which allows aligning linear expressions and dataarrays and variables.

Usage

>>> import linopy as lp
>>> m = lp.Model()
>>> x = m.add_variables(pd.Series([0, 0]), 1, name="x")
>>> alpha = xr.DataArray([1, 2], [[1, 2]])
>>> x_a, alpha = lp.align(x, alpha)
>>> x_a
Variable (dim_0: 1)
-------------------
[1]: x[1] ∈ [0, 1]

Alternative

Note that there would also be the alternative implementation strategy to implement the Alignable protocol for Variable and LinearExpression.

https://github.com/pydata/xarray/blob/852ad1135b9b8c46d8e301c9badbe898bd6d262d/xarray/core/types.py#L125-L166

but i did not test that, and i am unsure whether we could choose dimension exclusions that way.

Checklist

• Code changes are sufficiently documented; i.e. new functions contain docstrings and further explanations may be given in doc.
• Unit tests for new features were added (if applicable).
• A note for the release notes doc/release_notes.rst of the upcoming release is included.
• I consent to the release of this PR's code under the MIT license.