Errors on non-callable unions should be more specific

While working on #29011 I realized that the error we produce for unions of things which look callable but for which we cannot synthesize a signature for are lackluster. We report an error like:

Cannot use 'new' with an expression whose type lacks a call or construct signature.

when we could do better and say something like

Cannot use 'new' with an expression whose type lacks a call or construct signature. All members of union type {0} have call or construct signatures, but none are similar enough to resolve a call in a typesafe way.

which would make it far more clear what's going on in these scenarios.

Once #29011 is merged, the conditions can be even more specific, such as

Cannot use 'new' with an expression whose type lacks a call or construct signature. All members of union type {0} have call or construct signatures, but more than one has overloads, which prevents this call from being resolved in a typesafe way.

and

Cannot use 'new' with an expression whose type lacks a call or construct signature. All members of union type {0} have call or construct signatures, but more than one has type parameters, which prevents this call from being resolved in a typesafe way.

既存の診断 “Cannot use 'new' with an expression whose type lacks a call or construct signature” から始め、#29011 に併記されている関連条件を確認します。完了条件は、報告される union のケースで、合成できないシグネチャ、複数のオーバーロード、複数の型パラメーターを、示されているより具体的なメッセージで区別できることです。