fix: update eslint to use flat config (#1635)

[walter-0]

Which problem is this PR solving?

• Resolves Upgrade eslint to flat config #1635

Short description of the changes

• Upgrades eslint, @typescript-eslint, and all related plugins
• Rewrites the root eslint config to use the flat style
• Updates lint script in each package.json
• Removes all deprecated .eslintignores
• Removes all eslintrc.js files within each package
• Cleans up the eslint plugins and rules to remove deprecated ones
• Adds @copyright and @license JSDoc tags to header comment.

[linux-foundation-easycla]

• ✅login: walter-0 / (e003961)

The committers listed above are authorized under a signed CLA.

[walter-0]

Hi, I'm a new contributor and I have a couple of questions to get this ready.
I updated eslint and ran lint:fix on everything, but there are still some typescript related linting errors. Many of them are no-explicit-any, no-missing-import. What is the convention for type-related linting errors, and other code smells such as unused-vars, no-unsafe-function-type.
I think the no-missing-import may have something to do with the root tsconfig using moduleResolution: node, which probably should be considered deprecated since it's for Node versions older than v10. I wasn't able to get that working on my end, but perhaps there's something I'm not aware of with this project.

[github-actions]

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