[Draft] Update Eslint to the latest version 9

[carocao-msft]

What

Update Eslint to the latest version 9

Guides

Use the following command to convert the current eslint files to the new flat config file npx @eslint/migrate-config .eslintrc.json Run rushx lint to identify errors https://eslint.org/docs/latest/use/configure/migration-guide

Known Issue

https://github.com/Stuk/eslint-plugin-header/issues/57 Header/header rules no longer supported We can look into prettier for this issue

Random CI failure related to prettier https://github.com/prettier/eslint-plugin-prettier/issues/671#issuecomment-2312462407

Process & policy checklist

• [ ] I have updated the project documentation to reflect my changes if necessary.
• [ ] I have read the CONTRIBUTING documentation.

Is this a breaking change?

• [ ] This change causes current functionality to break.

[github-actions[bot]]

Chat bundle size is not changed.

• Current size: 1756438
• Base size: 1756438
• Diff size: 0

[github-actions[bot]]

Calling bundle size is not changed.

• Current size: 11750179
• Base size: 11750179
• Diff size: 0

[github-actions[bot]]

CallWithChat bundle size is not changed.

• Current size: 11750193
• Base size: 11750193
• Diff size: 0

[emlynmac]

superseded by #5866