feat(nodejs): improve eslint setup

[wpessers]

fixes #2158

Changes in this PR:

• Upgraded eslint to major version 9
• Upgraded gts to major version 7
• Removed @typescript-eslint/eslint-plugin and @typescript-eslint/parser, they are now bundled by gts
• Rewrote eslint config to use flat config, consolidating all subproject configs and .eslintignore files
• Applied formatting to .js, .cjs, .mjs files as well
• (re)formatted wherever necessary. Lots of changes to the dynamic imports' formatting in wrapper.ts due to an underlying upgrade of prettier: https://prettier.io/blog/2025/11/27/3.7.0#change-17882

[wpessers]

@pragmaticivan maybe you can take a look here, seeing your js expertise 🙂

[wpessers]

Or anyone else in @open-telemetry/lambda-extension-approvers who's eager to take a look 🙂

[maxday]

thannnks for doing this!