Import UInt8 from Base explicitely

[felixcremer]

This is to silence the warnings on Julia nightly:

 │  WARNING: Constructor for type "UInt8" was extended in `Zarr` without explicit qualification or import.
│    NOTE: Assumed "UInt8" refers to `Base.UInt8`. This behavior is deprecated and may differ in future versions.`
│    NOTE: This behavior may have differed in Julia versions prior to 1.12.
│    Hint: If you intended to create a new generic function of the same name, use `function UInt8 end`.
│    Hint: To silence the warning, qualify `UInt8` as `Base.UInt8` or explicitly `import Base: UInt8`

[felixcremer]

I looked at the failures but I don't understand what is happening. It seems as if the conversion from python to julia is massively broken.

[nhz2]

I have a PR #176 to switch from PyCall to PythonCall which seems to fix the CI