This changeset is motivated by a simple concept - get rid of the MiniYaml.Clone and MiniYamlNode.Clone methods to avoid deep copying yaml trees during merging. MiniYaml becoming immutable allows the merge function to reuse existing yaml trees rather than cloning them, saving on memory and improving merge performance. On initial loading the YAML for all maps is processed, so this provides a small reduction in initial loading time.
The rest of the changeset is dealing with the change in the exposed API surface. Some With* helper methods are introduced to allow creating new YAML from existing YAML. Areas of code that generated small amounts of YAML are able to transition directly to the immutable model without too much ceremony. Some use cases are far less ergonomic even with these helper methods and so a MiniYamlBuilder is introduced to retain mutable creation functionality. This allows those areas to continue to use the old mutable structures. The main users are the update rules and linting capabilities.
* Rename LeftColor and RightColor to MinColor and MaxColor
These are mapped from LowRadarColor and HighRadarColor in
the original inis, and appear to be used to set the bounding
values for selecting a random colour, NOT for left/right
pixels (which caused noticeably wrong banding).
* Adjust brightness based on terrain height.
MinHeightColorBrightness and MaxHeightColorBrightness
were chosen by trial/error to match the original
map preview rendering.
