Implement getters for Reclass.nodes and Reclass.classes

[simu]

This allows Python code to read basic information about the results of the node and classes discovery without having to render the inventory.

the new getters return dicts which map the normalized Reclass entity names (with dots for entities in subdirectories) to the file path associated with the entity.

Checklist

• The PR has a meaningful title. The title will be used to auto generate the changelog
• PR contains a single logical change (to build a better changelog).
• Update the documentation.
• Update tests.
• Categorize the PR by setting a good title and adding one of the labels:
  bug, enhancement, documentation, change, breaking, dependency, internal
  as they show up in the changelog

[haasad]

LGTM

expected_nodes = set([f"n{i}" for i in range(1, 26)])

this could also be written as set comprehension:

expected_nodes = {f"n{i}" for i in range(1, 26)}

😉

[github-actions]

Benchmark for 12f8127

Click to view benchmark

Test	Base	PR	%
Reclass::inventory() multi-threaded	1635.5±114.46µs	1629.4±85.19µs	-0.37%
Reclass::inventory() single-threaded	3.6±0.09ms	3.6±0.09ms	0.00%