Circular dependencies in ecschema-metadata

[rschili]

There are many circular dependencies in ecschema-metadata. Right now they do not seem to surface but minimal changes can make it into a problem.
For example Property.ts references concrete property implementations.

Paul introduced a fix for this in frontend 5 years back: 96878c5
That mechanism is described in this article: https://medium.com/visual-development/how-to-fix-nasty-circular-dependency-issues-once-and-for-all-in-javascript-typescript-a04c987cf0de

Another circular dependency that we have is:

ECClass -> ECProperty (getProperties, addProperty, createXXXProperty)
Property -> RelationshipClass (NavigationProperty)
RelationshipClass -> EntityClass (ConstraintClass)
EntityClass -> Mixin (getMixins)
Mixin -> ECClass (derives)

The problem surfaces at runtime, the compiler does not detect or warn about this.