feat: add in actions() to Problem

This adds a new field into `xsbti.Problem` allowing for the compiler to
forward "actions" that can address diagnostics. The idea largely mimics
a very minimal `CodeAction` that can be found in the [LSP
Spec](https://microsoft.github.io/language-server-protocol/specifications/lsp/3.17/specification/#codeAction)
in order to ensure it will work with a variety of difference clients
that use LSP, and those that don't. In the future the `WorkspaceEdit`
that was created here could also be expanded to handle more advanced
changes, aka resource operations, like creating/moving/deleting files.
For now we only focus on a small subset of these features.

internal/util-interface/src/main/java/xsbti/Action.java

@@ -0,0 +1,32 @@
+/*
+ * sbt
+ * Copyright 2011 - 2018, Lightbend, Inc.
+ * Copyright 2008 - 2010, Mark Harrah
+ * Licensed under Apache License 2.0 (see LICENSE)
+ */
+
+package xsbti;
+
+import java.util.Optional;
+
+/**
+ * An Action is very miminal representation of a `CodeAction` in the LSP protocol.
+ *
+ * <p>However it only focuses on the actual title, description, and edit, leaving it up to the
+ * language server to communicate with the client and put together a proper codeAction in accordance
+ * to client capabilities.
+ *
+ * @see <a href=
+ *     "https://microsoft.github.io/language-server-protocol/specifications/lsp/3.17/specification/#codeAction">`CodeAction`</a>
+ */
+public interface Action {
+
+  /** Title of the action that will be shown to the user client side. */
+  String title();
+
+  /** Optional description that may be shown to the user client side to explain the action. */
+  Optional<String> description();
+
+  /** The actual edit contained in the action. */
+  WorkspaceEdit edit();
+}