Re-enable running our eslint rules using ts-node (#159495)

Resubmission of #157532 with the following changes:

- Use `eslint-plugin-local` instead of `yarn` link to run our plugins
- Move our plugins to a top level `.eslintplugin` dir (as required by `eslint-plugin-local`)
- Update all names to `local/`

.eslintplugin/code-no-test-only.ts

@@ -0,0 +1,20 @@
+/*---------------------------------------------------------------------------------------------
+ *  Copyright (c) Microsoft Corporation. All rights reserved.
+ *  Licensed under the MIT License. See License.txt in the project root for license information.
+ *--------------------------------------------------------------------------------------------*/
+
+import * as eslint from 'eslint';
+
+export = new class NoTestOnly implements eslint.Rule.RuleModule {
+
+	create(context: eslint.Rule.RuleContext): eslint.Rule.RuleListener {
+		return {
+			['MemberExpression[object.name="test"][property.name="only"]']: (node: any) => {
+				return context.report({
+					node,
+					message: 'test.only is a dev-time tool and CANNOT be pushed'
+				});
+			}
+		};
+	}
+};