[Improvement]: Provide code actions to fix non-private mutable fields

[nipunayf]

Description

The fix for the diagnostic invalid non-private mutable field in an 'isolated' object(BCE3956) is straightforward, as we have to make the field private or make the field immutable. It would be convenient for a user if we could provide a code action as a quick fix for this use case.

Describe your problem(s)

No response

Describe your solution(s)

Consider the following source code with the respective diagnostic.

isolated class IsolatedClass {
    int i = 32;
}

FIX1: Allow the user to make the variable private.

isolated class IsolatedClass {
    private int i = 32; // changed
}

FIX2: Allow the user to make the variable immutable by making it final and readonly.

isolated class IsolatedClass {
    final int i = 32; // changed
}

Related area

-> Compilation

Related issue(s) (optional)

#28681

Suggested label(s) (optional)

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Suggested assignee(s) (optional)

No response