fix(tasks): #626 model task capabilities correctly

[alexhancock]

Fixes #626

Capabilities for tasks take the following form.

Client

{
  "capabilities": {
    "tasks": {
      "list": {},
      "cancel": {},
      "requests": {
        "sampling": {
          "createMessage": {}
        },
        "elicitation": {
          "create": {}
        }
      }
    }
  }
}

Server

{
  "capabilities": {
    "tasks": {
      "list": {},
      "cancel": {},
      "requests": {
        "tools": {
          "call": {}
        }
      }
    }
  }
}

We were previously using booleans to model these instead of objects, causing errors during initialization between servers and clients that expressed these capabilities

[jamadeo]

Nice! Works on my test with goose.

[jamadeo]

are these really testing all that much?

[alexhancock]

not terribly. the serialization one has value but these I agree don't add much. merging for not to not wait for another CI cycle but I will remove them on a future change.