Polishing: use readonly arrays

[johnsonr]

No description provided.

[ddgenome]

Won't this break the implementations of, for example, addExtentionPacks since it modifies the extensionPacks array?

[ddgenome]

Although I guess if the TypeScript compiler is not complaining…

[ddgenome]

It's strange that the interface defines ReadOnlyArrays

sdm/lib/api/machine/ListenerRegistrationManager.ts

Line 114 in 2226a27

readonly startupListeners: ReadonlyArray<StartupListener>;

but the compiler allows the implementation to use regular arrays that can be mutated

sdm/lib/api-helper/machine/ListenerRegistrationManagerSupport.ts

Line 40 in 2226a27

public readonly startupListeners: StartupListener[] = [];

and are mutated

sdm/lib/api-helper/machine/ListenerRegistrationManagerSupport.ts

Line 71 in 2226a27

this.startupListeners.push(l);

[johnsonr]

I assume that the implementation is seeing the mutable type. Whereas callers through the interface are constrained, which is the goal.

[ddgenome]

So the interface constrains the consumer and the implementer different ways. Intriguing.

[ddgenome]

LGTM