Rename `Result` to `TaskState`

`Loading` is a state, not a result. Result means an outcome. Something's outcome is always either `Success` or `Failure`. A `Failure` is **caused by** an error (a.k.a. `Throwable`).

A **task** can be in one of the following **states**;
- Not Started _(not useful)_
- Ongoing/In Progress
- Ended (either successfully or unsuccessfully)

A result of a task is also one of its states (Ended). Because of that, `Success` and `Failure` can easily be incorporated into `TakState`.

In the end, what we get is:

```kt
sealed interface TaskState {
data class Success(val data: T) : TaskState
data class Failure(val cause: Throwable) : TaskState
data object Ongoing : TaskState
}
```

If this is acceptable, let me know, I'll open a PR.

The issue names no files, tests, or entry points. Start by locating references to Result, Loading, Success, and Failure, then compare their current usage with the proposed TaskState model. Done would require an agreed design and consistent updates across the affected code and tests.

Written by the indexing model from the issue text.