Blender 2.9 LTS support

[MoritzBrueckner]

This is the main pull request for the transition to the upcoming Blender 2.9 LTS versions (issue). It will be in draft status as long as we're working on the migration and maybe even add some more features.

When contributing to the blender2.9 branch, please link to this pull request so that all related PRs are listed below this post. Thanks!

Checklist of critical tasks:

• Rigid bodies: steps_per_second was replaced by substeps_per_frame, leading to an error on export. Likely PhysicsWorld.hx needs to be changed as well or we need to convert the values during export if possible (Blender 2.9 Fix Exporter and conversions for Physics World #2084)
• The principled BSDF node has a new emission strength input, node indices might be wrong now ([Blender 2.9] Principled BSDF: update input socket indices #2081)
• Error when using the search operator menu (F3) ([Blender 2.9] Search menu fixes #2086):

  [...]/armory/blender\arm\props_tilesheet.py", line 93, in poll
      trait = wrd.arm_tilesheetlist[wrd.arm_tilesheetlist_index]
  IndexError: bpy_prop_collection[index]: index 0 out of range, size 0
  

• Error when using the search operator menu in the render properties tab (Fix lod operator polling and add some bl_options #2099)
• The new search menu might require some operators to be updated, only those who are exposed in the UI will be found unless explicitely stated: https://wiki.blender.org/wiki/Reference/Release_Notes/2.90/Python_API (Blender 2.9: Update operator options #2083)
• There were some general changes to UI layouts, for example the trait list and Armory player panel look weird in Blender 2.9 ([Blender 2.9] Object panel UI #2077, [Blender 2.9] Various UI improvements & redesigns #2093)
• Check if some icons changed (when there are some 2.93 builds released)
• Update the 2.83 LTS warning to 2.9 (Update Blender version information to 2.93 LTS #2176)
• Update the add-ons bl_info attribute ([Blender 2.9] Update Blender version information to 2.93 LTS armsdk#21)

The entire checklist of tasks can be found here: https://docs.google.com/spreadsheets/d/1uQsNnC2zD-NVYmVETWPj_or23QykmJkbRaSZDML5nHY/edit?usp=sharing

Additional, non-critical changes:

• [Blender 2.9] Update attribute node #2097 (Attribute node updates)
• [Blender 2.9] Nishita sky model & (ir)radiance support for all world shaders #2149 (Nishita sky model & irradiance)
• [Blender 2.9] Slightly improve debug console panel UI #2184 (Debug console panel UI)

Requires:

armory3d/iron#121.

[MoritzBrueckner]

Hi @luboslenco, I think this PR and armory3d/armsdk#21 are ready to merge if you agree :) Blender 2.93 LTS is scheduled for late May, so if everything goes according to plan the next Armory SDK can then support 2.9.

[luboslenco]

Super cool, thanks once again!