[Active learning] Merge main

[alexhernandezgarcia]

Merges main branch into activelearning branch.

Relevant changes:

• Environment and proxy are now detached.
• Branin now assumes that states are in [-1, 1] x [-1, 1] (instead of [0, 1]). This is too much the assumption in the Corners proxy and the default in the Grid and Cube environments.
• Hartmann also assumes that states are in [-1, 1]^6 (instead of [0, 1]^6).

To be done:

• Adapt Branin
• Adapt Hartmann
• Write tests for Branin and Hartmann using the environments.
• Update config files of Branin and Hartmann with new and default values