Refactor Weak Labelling Rule and Api structure

[ufukhurriyetoglu]

    Here, we have coupled components between `Rule` and `Api`. We've already had it with the `apply` method. We can go forward as is, but we will assume the technical debt. 

If in the future we allow defining contextualized clients, as the example shows:

with rb.init("<an-url>", "<an-api-key") as client:
   client.log..
   client.load...

We need to redesign all this stuff.

Just to keep in mind.

Originally posted by @frascuchon in #1884 (comment)

[ufukhurriyetoglu]

@frascuchon we can proceed with this issue at future iterations.

[github-actions]

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