Add helper set_text forwarding to ax.text()

What does this MR do?

This MR adds the plot_helper set_text that forwards to the matplotlib.pyplot.text function

Can this MR be accepted?

• Implemented new helper
• Tests added or adjusted
• Pipeline passes
• Changelog entry added
• Approved by @blsqr

Anything to double-check?

Changelog has to be set --- I forgot how to do that

Related issues

Closes #...