chore: consolidate eslint config

This change:

- Removes all `.eslintignore` , `.eslintrc` files or `package.json`-embedded config and replaces it with a single root `.eslintrc.js`
- Removes all lint-related scripts from all workspaces (including `depcheck`)
- Removes all dev deps on `eslint` and its ilk (and `ava`, since it will come from the workspace root)
- Upgrades `@metamask/eslint-config-nodejs`, `eslint`, `eslint-plugin-ava`, as well as other plugins used by specific packages; moves them all to workspace root
- Removes unused/deprecated `eslint-plugin-node` in lieu of `eslint-plugin-n`, which the new version of `@metamask/eslint-config-nodejs` needs
- Adds a prettier config (in case someone wants to use it; I'd like to add it to our workflow later)

I note that ESLint seemed to be misconfigured before this change; none of the rules specified in the root config were being checked.  This means that there are a whole lot of lint fixes that need to be made.

To lint, run `yarn lint` as before (which will also run `depcheck`) from the workspace root.  Likewise, `lint:fix` runs a fix, and `lint:depcheck` will use lerna to run `lint:depcheck` wherever it is defined.

.eslintrc.js

@@ -0,0 +1,116 @@
+module.exports = {
+  root: true,
+  // this is the same as an .eslintignore file
+  ignorePatterns: [
+    '.yarn/**/*',
+    '**/*.umd.js',
+    '**/node_modules/**/*',
+    'docs/**/*',
+    'packages/*/examples/**/*',
+    'packages/*/test/**/fixtures/**/*',
+    'packages/*/test/projects/**/*',
+    'packages/lavapack/bundle.js',
+    'packages/lavapack/src/runtime-cjs.js',
+    'packages/lavapack/src/runtime.js',
+    'packages/perf/trials/**/*',
+    'packages/survey/mitm/**/*',
+    'packages/viz/dist/**/*',
+    'packages/viz/src/example-policies/**/*',
+  ],
+  parserOptions: {
+    // this should be whatever the latest env version provides. some plugin is
+    // messing with this, so we need to set it manually.
+    // https://eslint.org/docs/latest/use/configure/language-options#specifying-environments
+    ecmaVersion: 12,
+  },
+  env: { es2020: true }, // this should be synced with the version of V8 used by the min supported node version
+  extends: ['@metamask/eslint-config-nodejs'],
+  rules: {
+    // base rules. should probably use eslint/recommended instead.
+    'arrow-spacing': ['error', { before: true, after: true }],
+    'brace-style': ['error', '1tbs'],
+    'comma-dangle': ['error', 'always-multiline'],
+    curly: ['error', 'all'],
+    'eol-last': ['error', 'always'],
+    indent: ['error', 2, { SwitchCase: 1, ObjectExpression: 'first' }],
+    'no-restricted-globals': 0,
+    'no-unexpected-multiline': 'error',
+    quotes: ['error', 'single'],
+    semi: ['error', 'never'],
+    'space-before-blocks': ['error', 'always'],
+    'space-before-function-paren': [
+      'error',
+      {
+        anonymous: 'ignore',
+        named: 'ignore',
+        asyncArrow: 'always',
+      },
+    ],
+
+    // plugin rules
+
+    // all of these override stuff set in @metamask/eslint-config-nodejs.
+    'n/no-extraneous-require': 0,
+    'n/global-require': 0,
+    'n/exports-style': 0,
+    'n/no-process-env': 0,
+    // this rule seems broken
+    'n/no-unpublished-require': 0,
+    // we should probably actually fix these three and disable this override.
+    'n/no-sync': 0,
+    'n/no-process-exit': 0,
+    'n/no-path-concat': 0,
+  },
+  // these are plugin-specific settings.
+  settings: {
+    // note that this name is "node" while the plugin is named "n".
+    // probably for historical reasons, but this may eventually break.
+    node: {
+      version: '14.17.0', // should be set to minimum node version supported
+      allowModules: ['deep-equal'], // something weird about this dependency
+    },
+    react: {
+      version: 'detect',
+    },
+  },
+  overrides: [
+    {
+      files: ['packages/*/test/**/*.js', 'packages/*/src/**/*.test.js'],
+      extends: ['plugin:ava/recommended'],
+      rules: {
+        'ava/no-import-test-files': 0,
+      },
+    },
+    {
+      files: ['packages/core/src/**/*.js'],
+      globals: {
+        Compartment: 'readonly',
+        templateRequire: 'readonly',
+        lockdown: 'readonly',
+      },
+    },
+    {
+      // for viz package.  most of this copied out of its own eslint config
+      files: ['packages/viz/**/*.js'],
+      env: {
+        browser: true,
+        es2020: true,
+      },
+      parserOptions: {
+        ecmaFeatures: {
+          jsx: true,
+        },
+        sourceType: 'module',
+      },
+      extends: ['plugin:react/recommended'],
+      plugins: ['react', 'import'],
+      rules: {
+        'no-negated-condition': 0,
+        'import/extensions': ['error', 'always', { ignorePackages: true }],
+        'import/no-unassigned-import': 0,
+        'import/unambiguous': 0,
+        'react/prop-types': 0,
+      },
+    },
+  ],
+}