Python graph attributes: add implicit conversion from int to float

[bernlu]

Python currently does not implicitly convert integer literals to float when using float graph attributes:

g = nk.Graph(1)
attr = g.attachNodeAttribute('test', float)
attr[0] = 0

---------------------------------------------------------------------------
Exception                                 Traceback (most recent call last)
Cell In[4], [line 3](vscode-notebook-cell:?execution_count=4&line=3)
      [1](vscode-notebook-cell:?execution_count=4&line=1) g = nk.Graph(1)
      [2](vscode-notebook-cell:?execution_count=4&line=2) attr = g.attachNodeAttribute('test', float)
----> [3](vscode-notebook-cell:?execution_count=4&line=3) attr[0] = 0

File .venv/lib/python3.10/site-packages/networkit/graph.pyx:1372, in networkit.graph.NodeAttribute.__setitem__()

Exception: Wrong Attribute type

running the same code with attr[0] = 0. works.