Motivation / Problem

Creating rainforest in the scenario editor is exceptionally hard. The only way to make a rainforest is to plant a rainforest tree with the single-tile tree brush. See also #9241

Description

This PR allows larger tree brushes to also create rainforest tiles. The behavior of random-tree brushes remains unchanged.

Limitations

Currently, the implementation simply makes the behavior of the larger tree brushes match that of the single-tile brush. However, the zoning could be more complex (such as planting cacti also creates desert or such).

Checklist for review

Some things are not automated, and forgotten often. This list is a reminder for the reviewers.

• The bug fix is important enough to be backported? (label: 'backport requested')
• This PR touches english.txt or translations? Check the guidelines
• This PR affects the save game format? (label 'savegame upgrade')
• This PR affects the GS/AI API? (label 'needs review: Script API')
  • ai_changelog.hpp, gs_changelog.hpp need updating.
  • The compatibility wrappers (compat_*.nut) need updating.
• This PR affects the NewGRF API? (label 'needs review: NewGRF')
  • newgrf_debug_data.h may need updating.
  • PR must be added to API tracker