fix!: Tighten and correct typings on ASTNode

[gonfunko]

The basics

• I validated my changes

The details

Resolves

Fixes #8827

Proposed Changes

This PR updates most of the static ASTNode.create*Node() methods to not check for null arguments (which their method signature prohibits) and not (claim to) return null when that only happened in the case of an invalid null argument. I also cleaned up several unsafe casts and non-null assertions and corrected some other typings.

Breaking Changes

• The type signature of ASTNode.getWsCoordinate() now allows for null return types, which were always possible but not part of the return type before
• createWorkspaceNode() no longer allows null workspace or coordinate arguments; it would have just returned null had either of those been provided, so callers check for that and do whatever they would have done had the return value been null.

[rachel-fenichel]

One more piece of cleanup, plus whatever is going on with the conventional commit labeler, and then good to go.

[gonfunko]

The commit labeler is just busted here because this is targeting v12 and the action fix isn't there yet. I manually assigned the appropriate labels.