web: update to ESLint 9 (#10812)

* web: update to ESLint 9

ESLint 9 has been out for awhile now, and all of the plug-ins that we use have caught up, so it is
time to bite the bullet and upgrade.  This commit:

- upgrades to ESLint 9, and upgrades all associated plugins
- Replaces the `.eslintrc` and `.eslintignore` files with the new, "flat" configuration file,
  "eslint.config.mjs".
- Places the previous "precommit" and "nightmare" rules in `./scripts/eslint.precommit.mjs` and
  `./scripts/eslint.nightmare.mjs`, respectively
- Replaces the scripted wrappers for eslint (`eslint`, `eslint-precommit`) with a single executable
  that takes the arguments `--precommit`, which applies a stricter set of rules, and `--nightmare`,
  which applies an even more terrifyingly strict set of rules.
- Provides the scripted wrapper `./scripts/eslint.mjs` so that eslint can be run from `bun`, if one
  so chooses.
- Fixes *all* of the lint `eslint.config.mjs` now finds, including removing all of the `eslint`
  styling rules and overrides because Eslint now proudly leaves that entirely up to Prettier.

To shut Dependabot up about ESLint.

* Added explanation for no-console removal.

* web: did not need the old and unmaintained nightmare mode; it can be configured directly.

web/scripts/eslint-nightmare.mjs

@@ -1,55 +0,0 @@
-import { execFileSync } from "child_process";
-import { ESLint } from "eslint";
-import path from "path";
-import process from "process";
-
-// Code assumes this script is in the './web/scripts' folder.
-const projectRoot = execFileSync("git", ["rev-parse", "--show-toplevel"], {
-    encoding: "utf8",
-}).replace("\n", "");
-process.chdir(path.join(projectRoot, "./web"));
-
-const eslintConfig = {
-    overrideConfig: {
-        env: {
-            browser: true,
-            es2021: true,
-        },
-        extends: [
-            "eslint:recommended",
-            "plugin:@typescript-eslint/recommended",
-            "plugin:lit/recommended",
-            "plugin:custom-elements/recommended",
-            "plugin:storybook/recommended",
-            "plugin:sonarjs/recommended",
-        ],
-        parser: "@typescript-eslint/parser",
-        parserOptions: {
-            ecmaVersion: 12,
-            sourceType: "module",
-        },
-        plugins: ["@typescript-eslint", "lit", "custom-elements", "sonarjs"],
-        rules: {
-            "indent": "off",
-            "linebreak-style": ["error", "unix"],
-            "quotes": ["error", "double", { avoidEscape: true }],
-            "semi": ["error", "always"],
-            "@typescript-eslint/ban-ts-comment": "off",
-            "sonarjs/cognitive-complexity": ["error", 9],
-            "sonarjs/no-duplicate-string": "off",
-            "sonarjs/no-nested-template-literals": "off",
-        },
-    },
-};
-
-const updated = ["./src/", "./build.mjs", "./scripts/*.mjs"];
-
-const eslint = new ESLint(eslintConfig);
-const results = await eslint.lintFiles(updated);
-const formatter = await eslint.loadFormatter("stylish");
-const resultText = formatter.format(results);
-const errors = results.reduce((acc, result) => acc + result.errorCount, 0);
-
-// eslint-disable-next-line no-console
-console.log(resultText);
-process.exit(errors > 1 ? 1 : 0);