additional scalings and new parser constructor

[jucordero]

Description

This pull request introduces new functions which can be used as temporal profiles for the different scaling models in agrifoodpy

It also registers these scaling functions with the custom !scale tag to be used in yaml configuration files.
e.g.

nodes:
  - function: agrifoodpy.utils.nodes.write_to_datablock
    name: Write a linear profile to the datablock
    params:
      key: linear_scale
      value: !scale.linear_scale [2025, 2030, 2040, 2050, 1, 1.5]

Checklist

• Follow the Contributor Guidelines
• Write unit tests
• Write documentation strings