tools: enable stricter linting in lib directory

Enable ESLint 4.x linting and disable legacy linting in the lib
directory.

While doing this, some indentation in the .eslintrc.yaml file itself was
noticed to be incorrect. Fixed that too.

PR-URL: #14403
Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: Yuta Hiroto <hello@about-hiroppy.com>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Evan Lucas <evanlucas@me.com>
Reviewed-By: Timothy Gu <timothygu99@gmail.com>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Refael Ackermann <refack@gmail.com>
Reviewed-By: Alexey Orlenko <eaglexrlnk@gmail.com>

.eslintrc.yaml

@@ -102,17 +102,17 @@ rules:
   func-name-matching: error
   func-style: [error, declaration, {allowArrowFunctions: true}]
   # indent: [error, 2, {ArrayExpression: first,
-  #                 CallExpression: {arguments: first},
-  #                 FunctionDeclaration: {parameters: first},
-  #                 FunctionExpression: {parameters: first},
-  #                 MemberExpression: off,
-  #                 ObjectExpression: first,
-  #                 SwitchCase: 1}]
+  #                     CallExpression: {arguments: first},
+  #                     FunctionDeclaration: {parameters: first},
+  #                     FunctionExpression: {parameters: first},
+  #                     MemberExpression: off,
+  #                     ObjectExpression: first,
+  #                     SwitchCase: 1}]
   indent-legacy: [error, 2, {ArrayExpression: first,
-                         CallExpression: {arguments: first},
-                         MemberExpression: 1,
-                         ObjectExpression: first,
-                         SwitchCase: 1}]
+                             CallExpression: {arguments: first},
+                             MemberExpression: 1,
+                             ObjectExpression: first,
+                             SwitchCase: 1}]
   key-spacing: [error, {mode: minimum}]
   keyword-spacing: error
   linebreak-style: [error, unix]

lib/.eslintrc.yaml

@@ -1,4 +1,13 @@
 rules:
+  indent: [error, 2, {ArrayExpression: first,
+                      CallExpression: {arguments: first},
+                      FunctionDeclaration: {parameters: first},
+                      FunctionExpression: {parameters: first},
+                      MemberExpression: off,
+                      ObjectExpression: first,
+                      SwitchCase: 1}]
+  indent-legacy: 0
+
   # Custom rules in tools/eslint-rules
   require-buffer: error
   buffer-constructor: error