Unify property get/set/init/readonly statuses

[Ernest314]

This includes using things like public object Data { get => Object.Data; } instead of public object Data => Object.Data;.

Edit: These two are actually equivalent.

[Ernest314]

Also initialize properties as such where possible:

public List<string> Data { get; } = new ();

[Ernest314]

readonly should only modify fields (not properties) and structs (including record structs)--avoid using in other contexts.

See:

• https://learn.microsoft.com/en-us/dotnet/csharp/language-reference/keywords/readonly
• https://learn.microsoft.com/en-us/dotnet/csharp/language-reference/builtin-types/struct#readonly-struct