Change: rearrange definitions of tree info to remove hardcoded values

[PeterN]

Motivation / Problem

Trees are full of magic. Magic sprite numbers, magic climate-based value and magic tropic-zone values.

De-magic them.

Description

Rearrange definitions of tree info to remove hardcoded values
Tree availability is now defined with climates and tropical zone.

Limitations

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 GS/AI API? (label 'needs review: Script API')
  • ai_changelog.hpp, game_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