Dyno: Improve initializers on classes that inherit

[benharsh]

This PR improves support for initializers on classes that inherit. With this commit dyno now supports:

• implicit 'super.init' calls
• errors for accessing parent fields before 'super.init'
• usage of initialized fields part-way through initializing the whole type

This PR updates the Resolver to rely somewhat less on 'InitResolver' for explicitly handling Identifier and Dot uAST nodes. Instead we continue to rely on established Resolver mechanisms and selectively invoke the InitResolver when appropriate.

This PR also improves a fix within 'handleCallExpr' originally meant to support receiver-less 'init' calls. Instead, this fix is adapted to any 'init' call within an initializer, and will replace or create the receiver using a fully-generic type. This is done in case the user has erroneously initialized fields prior to the explicit 'init' call. I plan on moving this behavior into InitResolver in the future.

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The fieldIdFromPossibleMentionOfField helper method is updated to return a field ID (if found) and whether that field is a parent field.

Some logic from handleCallToSuperInit is split off into a new updateSuperType method to better support the implicit 'super.init' case.

Minor fixes to findFieldByName

• Use VarLikeDecl instead, as NamedDecl can match primary methods.
• Do not continue searching upwards if the parent class is the root class.

Lastly, this commit adds tests for newly supported initializer behavior.

• test-dyno