Do not set valueDeclaration for intersection properties when one symbol does not have a valueDeclaration

[mdm317]

Fixes #61743
This issue arised because the intersection types are different.

declare class X {
	private a: number;
	b: string;
}
type Y = { a: number } & { b: string };
type Z = Pick<{ a: number }, 'a'> & { b: string };
type T1 = X & Y // T1 is never
type T2 = X & Z // but T2 is not never

[mdm317]

In isConflictingPrivateProperty, if symbols are not uniform and has private properties, determine property is conflict

    function isConflictingPrivateProperty(prop: Symbol) {
        // Return true for a synthetic property with multiple declarations, at least one of which is private.
        return !prop.valueDeclaration && !!(getCheckFlags(prop) & CheckFlags.ContainsPrivate);
    }

Currently, a intersection/uniform property is treated as uniform when one source property has a valueDeclaration, while another source property(mapped type) does not.
I think we should treat such properties as non-uniform instead.

[mdm317]

@microsoft-github-policy-service agree