Clean up Widgets

* Move /Widgets/Live/* to /Live/*
* Move /Widgets/Prompt/* to /Prompts/*
* Move tests and expectations to match the new locations

src/Spectre.Console/Live/Progress/ProgressContext.cs

@@ -0,0 +1,87 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+
+namespace Spectre.Console
+{
+    /// <summary>
+    /// Represents a context that can be used to interact with a <see cref="Progress"/>.
+    /// </summary>
+    public sealed class ProgressContext
+    {
+        private readonly List<ProgressTask> _tasks;
+        private readonly object _taskLock;
+        private readonly IAnsiConsole _console;
+        private readonly ProgressRenderer _renderer;
+        private int _taskId;
+
+        /// <summary>
+        /// Gets a value indicating whether or not all started tasks have completed.
+        /// </summary>
+        public bool IsFinished => _tasks.Where(x => x.IsStarted).All(task => task.IsFinished);
+
+        internal ProgressContext(IAnsiConsole console, ProgressRenderer renderer)
+        {
+            _tasks = new List<ProgressTask>();
+            _taskLock = new object();
+            _console = console ?? throw new ArgumentNullException(nameof(console));
+            _renderer = renderer ?? throw new ArgumentNullException(nameof(renderer));
+        }
+
+        /// <summary>
+        /// Adds a task.
+        /// </summary>
+        /// <param name="description">The task description.</param>
+        /// <param name="autoStart">Whether or not the task should start immediately.</param>
+        /// <param name="maxValue">The task's max value.</param>
+        /// <returns>The newly created task.</returns>
+        public ProgressTask AddTask(string description, bool autoStart = true, double maxValue = 100)
+        {
+            return AddTask(description, new ProgressTaskSettings
+            {
+                AutoStart = autoStart,
+                MaxValue = maxValue,
+            });
+        }
+
+        /// <summary>
+        /// Adds a task.
+        /// </summary>
+        /// <param name="description">The task description.</param>
+        /// <param name="settings">The task settings.</param>
+        /// <returns>The newly created task.</returns>
+        public ProgressTask AddTask(string description, ProgressTaskSettings settings)
+        {
+            if (settings is null)
+            {
+                throw new ArgumentNullException(nameof(settings));
+            }
+
+            lock (_taskLock)
+            {
+                var task = new ProgressTask(_taskId++, description, settings.MaxValue, settings.AutoStart);
+
+                _tasks.Add(task);
+
+                return task;
+            }
+        }
+
+        /// <summary>
+        /// Refreshes the current progress.
+        /// </summary>
+        public void Refresh()
+        {
+            _renderer.Update(this);
+            _console.Write(new ControlCode(string.Empty));
+        }
+
+        internal IReadOnlyList<ProgressTask> GetTasks()
+        {
+            lock (_taskLock)
+            {
+                return new List<ProgressTask>(_tasks);
+            }
+        }
+    }
+}