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/src/elements/ak-checkbox-group/ak-checkbox-group.ts

@@ -136,7 +136,6 @@ export class CheckboxGroup extends AkElementWithCustomEvents {
     constructor() {
         super();
         this.onClick = this.onClick.bind(this);
-        this.dataset.akControl = "true";
     }
 
     onClick(ev: Event) {
@@ -173,6 +172,7 @@ export class CheckboxGroup extends AkElementWithCustomEvents {
 
     connectedCallback() {
         super.connectedCallback();
+        this.dataset.akControl = "true";
         if (this.name && !this.internals) {
             this.internals = this.attachInternals();
         }