fix: make internally-invoked built-in transforms overridable

[timfish]

Built-in transforms called each other by direct reference on the module object (e.g. tracingChannelDeclaration → tracingChannelImport), so custom transforms registered via addTransform were bypassed on those internal calls.

Internal calls now dispatch through a merged transforms map (built-ins plus registered overrides) carried on state.transforms, so overriding any built-in transform including tracingChannelImport and tracingChannelDeclaration takes effect everywhere.

Moving the transforms to the state also allows transforms to chain other transforms.

Why might anyone want to override these?

Orchestrion currently only handles the publishing side of the diagnostics channel. It would be great to conditionally initialise the subscriber side too. This change would allow us to override tracingChannelImport to inject our initialisation code.

[isaacs]

(not the change being made here, I realize, but the same line) shouldn't this be moduleType? Doesn't seem to match the code it's about.

[rochdev]

Technically, anything can be added to the state. Would that be a problem if a user of the library is also using TypeScript?

[timfish]

Good point. I've improved the types to:

export type KnownState = InstrumentationConfig & {
    dcModule: string;
    moduleType: ModuleType;
    moduleVersion: string;
    operator: string;
    transforms: Record<string, CustomTransform>;
    functionIndex?: number;
};

export type CustomTransform<ExtraState = Record<string, unknown>> = (state: KnownState & ExtraState, node: Node, parent: Node, ancestry: Node[]) => void;

This means that downstream users can:

• Discover and access all the known properties
• Set/get any other properties freely (due to Record<string, unknown> default generic type)
• Override the generic type to make accessing of their custom state more type-safe