[JsonRpc Protocol] Separate location.method to location.method-name and location.method-parameters

One challenge in F# is its identifier name rules, where `(` for example is allowed. That means that clients cannot separate method name from parameter types.

I strongly believe that for MTP we should separate location.method to 2 different properties, matching the model of TestMethodIdentifierProperty. This means we don't need the escaping rules of ManagedMethod, and we are not forcing framework authors to implement the escaping logic and plug it in TestMethodIdentifierProperty for no good reason.

It's probably even better to separate it to 3 properties, `location.method-name`, `location.method-arity`, and `location.method.parameters`. This will require a public API change to TestMethodIdentifierProperty.

Start by locating the JsonRpc `location.method` representation and the `TestMethodIdentifierProperty` API referenced in the issue. Compare the proposed two-property and three-property models, then confirm the protocol and public API changes needed; done means an agreed property shape without requiring framework authors to implement escaping logic.

Written by the indexing model from the issue text.