Split up test project

Robust.UnitTesting was both ALL tests for RT, and also API surface for content tests.

Tests are now split into separate projects as appropriate, and the API side has also been split off.

Robust.Shared.Testing/TestLogHandler.cs

@@ -0,0 +1,48 @@
+using System.Diagnostics;
+using NUnit.Framework;
+using Robust.Shared.Configuration;
+using Robust.Shared.Log;
+using Serilog.Events;
+
+// ReSharper disable once CheckNamespace
+namespace Robust.UnitTesting
+{
+    public sealed class TestLogHandler : ILogHandler
+    {
+        private readonly string? _prefix;
+        private readonly TextWriter _writer;
+        private readonly Stopwatch _sw = Stopwatch.StartNew();
+
+        public TestLogHandler(IConfigurationManager cfg, string? prefix = null, TextWriter? testOutput = null)
+        {
+            cfg.OnValueChanged(RTCVars.FailureLogLevel, value => FailureLevel = value, true);
+
+            _prefix = prefix;
+            _writer = testOutput ?? TestContext.Out;
+            _writer.WriteLine($"{GetPrefix()}Started {DateTime.Now:o}");
+        }
+
+        private LogLevel? FailureLevel { get; set; }
+
+        public void Log(string sawmillName, LogEvent message)
+        {
+            var level = message.Level.ToRobust();
+            var name = LogMessage.LogLevelToName(level);
+            var seconds = _sw.ElapsedMilliseconds / 1000d;
+            var rendered = message.RenderMessage();
+            var line = $"{GetPrefix()}{seconds:F3}s [{name}] {sawmillName}: {rendered}";
+            _writer.WriteLine(line);
+
+            if (FailureLevel == null || level < FailureLevel)
+                return;
+
+            _writer.Flush();
+            Assert.Fail($"{line} Exception: {message.Exception}");
+        }
+
+        private string GetPrefix()
+        {
+            return _prefix != null ? $"{_prefix}: " : "";
+        }
+    }
+}