Update eslint-plugin-yml to 3.x

Problem/Motivation

This was deferred from #3621277: Update JavaScript dependencies for 12.0.0-beta1. The key problem is core main is using eslint-plugin-yml 1.19.1 from December 2025. The current release is 3.8.1 two, two major versions later.

v2.0.0 is ESM-only, exports flat config as the main format, keeps the flat/* names, and requires ESLint 9.38 and Node 20.19 or newer.
v3.0.0 makes the shareable configs use ESLint's language config API, language: "yml/yaml", instead of a parser in languageOptions.

Unfortunately the current release now uses ES2021 syntax while core lint with ES2020. So the plugin fails when linted. Even though its a third party plugin, eslint-plugin-import's import/default rule parses imported modules also in third party plugins. But linting the eslint-plugin-yml's eslint.config.mjs fails.

Steps to reproduce

Proposed resolution

Various options.

• We can update the package and turn off the import/default rule or
• Update and exclude the eslint-plugin-yml code from being linted entirely.
• Or update core's ES syntax to 2021 instead of 2020.
• Or do an update for an in-between release which is not current.
• And probably other options :)

Remaining tasks

User interface changes

Introduced terminology

API changes

Data model changes

Release notes snippet