Further validation of v3 fill values

[jhamman]

This adds an additional check that the provided fill value is representable by the dtype of an array. Previously, the following behavior was allowed,

In [3]: a = zarr.create(shape=(2, 2), dtype='uint8', fill_value=22.5)

In [4]: a.fill_value
Out[4]: np.uint8(22)

In this case, the dtype was silently converted to a int type 😢 .

Built on top of #2209
TODO:

• Add unit tests and/or doctests in docstrings
• Add docstrings and API docs for any new/modified user-facing classes and functions
• New/modified features documented in docs/tutorial.rst
• Changes documented in docs/release.rst
• GitHub Actions have all passed
• Test coverage is 100% (Codecov passes)

[jhamman]

merged into #2209.