Fix casting to float when assigning numeric values; fixes normalization of integer arrays

[eroell]

PR Checklist

• This comment contains a description of changes (with reason)
• Referenced issue is linked Fixes Scaling integer array does not cast to float #836
• If you've fixed a bug or added code that should be tested, add tests!
• Documentation in docs is updated

Description of changes
Newly, casting adata.X to the dtype of the array it is assigned values from.

Technical details
adata.X being of a dtype which annot be casted to the dtype of values (e.g. object if containing string) should not be a prominent problem, as this will trigger the set_numeric_values earlier during _assert_encoded.

Additional context

[Zethson]

Thank you!

[Zethson]

Resolved 264 packages in 3.18s
  × Failed to download and build `numpy==1.25.2`
  ╰─▶ Build backend failed to determine requirements with `build_wheel()`
      (exit status: 1)

      [stderr]
      Traceback (most recent call last):
        File "<string>", line 8, in <module>
        File
      "/home/docs/.cache/uv/builds-v0/.tmpFdZf6K/lib/python3.12/site-packages/setuptools/__init__.py",
      line 10, in <module>
          import distutils.core
      ModuleNotFoundError: No module named 'distutils'

      hint: `distutils` was removed from the standard library in Python 3.12.
      Consider adding a constraint (like `numpy >1.25.2`) to avoid building a
      version of `numpy` that depends on `distutils`.
  help: `numpy` (v1.25.2) was included because `ehrapy` (v0.11.0) depends on
        `lifelines` (v0.30.0) which depends on `numpy`

Why the heck is this happening now again. Sigh...