ci: Introduce no-plain-errors lint rule for BE packages (no-changelog) (#7961)

## Summary
Require `ApplicationError` or its child classes instead of plain `Error`
in BE packages. This ensures the error will be normalized when reported
to Sentry, if applicable.

Follow-up to:
https://github.com/n8n-io/n8n/pulls?q=is%3Apr+is%3Aclosed+applicationerror

...

#### How to test the change:
1. ...


## Issues fixed
Include links to Github issue or Community forum post or **Linear
ticket**:
> Important in order to close automatically and provide context to
reviewers

...


## Review / Merge checklist
- [ ] PR title and summary are descriptive. **Remember, the title
automatically goes into the changelog. Use `(no-changelog)` otherwise.**
([conventions](https://github.com/n8n-io/n8n/blob/master/.github/pull_request_title_conventions.md))
- [ ] [Docs updated](https://github.com/n8n-io/n8n-docs) or follow-up
ticket created.
- [ ] Tests included.
> A bug is not considered fixed, unless a test is added to prevent it
from happening again. A feature is not complete without tests.
  >
> *(internal)* You can use Slack commands to trigger [e2e
tests](https://www.notion.so/n8n/How-to-use-Test-Instances-d65f49dfc51f441ea44367fb6f67eb0a?pvs=4#a39f9e5ba64a48b58a71d81c837e8227)
or [deploy test
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packages/@n8n_io/eslint-config/base.js

@@ -330,7 +330,7 @@ const config = (module.exports = {
 			{
 				selector: 'import',
 				format: ['camelCase', 'PascalCase'],
-			}
+			},
 		],
 
 		// ----------------------------------
@@ -360,6 +360,7 @@ const config = (module.exports = {
 		// ----------------------------------
 		//   eslint-plugin-n8n-local-rules
 		// ----------------------------------
+
 		'n8n-local-rules/no-uncaught-json-parse': 'error',
 
 		'n8n-local-rules/no-json-parse-json-stringify': 'error',
@@ -370,6 +371,8 @@ const config = (module.exports = {
 
 		'n8n-local-rules/no-unused-param-in-catch-clause': 'error',
 
+		'n8n-local-rules/no-plain-errors': 'error',
+
 		// ******************************************************************
 		//                    overrides to base ruleset
 		// ******************************************************************
@@ -469,6 +472,7 @@ const config = (module.exports = {
 		{
 			files: ['test/**/*.ts', 'src/__tests__/*.ts'],
 			rules: {
+				'n8n-local-rules/no-plain-errors': 'off',
 				'n8n-local-rules/no-skipped-tests':
 					process.env.NODE_ENV === 'development' ? 'warn' : 'error',