[NodeJS] Support 'typesVersions' in node/v6 through node/v9 (#34678)

* Split node/v8 and node/v9

* Split node/v7 and add typesVersions

* Split node/v6 and add typesVersions

* Revert major file split but preserve 'typesVersions' support for v6-v9

types/node/v6/package.json

@@ -0,0 +1,11 @@
+{
+    "private": true,
+    "types": "index",
+    "typesVersions": {
+        ">=3.2.0-0": {
+            "*": [
+                "ts3.2/*"
+            ]
+        }
+    }
+}

types/node/v6/ts3.2/index.d.ts

@@ -0,0 +1,15 @@
+// NOTE: These definitions support NodeJS and TypeScript 3.2.
+
+// NOTE: TypeScript version-specific augmentations can be found in the following paths:
+//          - ~/base.d.ts         - Shared definitions common to all TypeScript versions
+//          - ~/index.d.ts        - Definitions specific to TypeScript 2.1
+//          - ~/ts3.2/index.d.ts  - Definitions specific to TypeScript 3.2
+
+// Reference required types from the default lib:
+/// <reference lib="es2015" />
+
+// Base definitions for all NodeJS modules that are not specific to any version of TypeScript:
+// tslint:disable-next-line:no-bad-reference
+/// <reference path="../base.d.ts" />
+
+// TypeScript 3.2-specific augmentations: