Large StateVector and DensityMatrix results cannot be serialized efficiently in `GateModelTaskResult`

## Problem

Large analytical result types from the default simulator are efficient while they stay in the current process, but they don't serialize efficiently through `GateModelTaskResult`.

`StateVector` and `DensityMatrix` return `np.ndarray` values, and `_generate_results()` stores those arrays directly in `ResultTypeValue.value`. That works for local `LocalSimulator(...).run(...).result()` because the ndarray can pass through as a Python object.

The problem appears at a JSON boundary, for example when persisting a raw result, round tripped through `GateModelTaskResult.parse_raw(...)`, or emitting a simulator result envelope from another process. `ResultTypeValue.value` is currently `list | float | dict`, with no compact ndarray representation. A raw ndarray is not JSON serializable, and converting it to lists causes a large memory blowup.

Full density matrices are worse because they scale as `16 * 4^n` bytes before serialization overhead.

## Proposed fix

Add an optional binary ndarray payload to `ResultTypeValue`, for example:

```python
class ResultTypeValue(BaseModel):
type: Results
value: list | float | dict | None = None

binaryValue: str | None = None
binaryEncoding: Literal["base64"] | None = None
dtype: Literal["complex64", "complex128", "float64"] | None = None
shape: list[int] | None = None
```

Use base64 text rather than raw `bytes`, since arbitrary ndarray bytes are not guaranteed to be valid UTF-8 under pydantic v1 JSON serialization.

For `StateVector` and `DensityMatrix`, the simulator can populate `binaryValue`, `dtype`, and `shape` instead of expanding the ndarray into `value`. SDK consumers can prefer `binaryValue` when present and fall back to `value` for backward compatibility.

## Scope

In scope:

- `StateVector`
- full or reduced `DensityMatrix`
- schema support in `ResultTypeValue`
- SDK decode path from `binaryValue`
- default simulator encode path

Out of scope:

- expectation, variance, sample, and amplitude result types
- changing the local in-process fast path
- side-channel storage by URI, which may still be useful for very large results

## Benefits

The simulator core can produce these results, but the result envelope becomes the limiting factor once serialization is required.