chore(webpack): further simplify our config

[LeoMcA]

Summary

https://mozilla-hub.atlassian.net/browse/MP-1132
Follow up to #11099

Problem

Our webpack and client dev config is overcomplicated as a result of using create react app.

Solution

Rip out things we're not using, hard code options, use defaults where they're good enough:

• chore(webpack): remove DISABLE_NEW_JSX_TRANSFORM option
• chore(webpack): remove FAST_REFRESH option
• chore(webpack): remove InterpolateHtmlPlugin
• chore(webpack): remove ModuleScopePlugin
• chore(webpack): remove ModuleNotFoundPlugin
• chore(webpack): directly import fork-ts-checker-webpack-plugin
• chore(webpack): remove create-react-app eslint config, use defaults
• chore(webpack): import chalk directly
• chore(webpack): remove react-dev-utils imports from build script
• chore(webpack): remove react-dev-utils imports from start script
• chore(webpack): remove react-dev-utils imports from dev server config
• chore(webpack): remove remnants of PUBLIC_URL and hard code
• chore(webpack): remove react-dev-utils

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How did you test this change?

No change to our prod code can be verified:

git checkout 4249546243cc16def100bfd2800dbecc6a9056b0
yarn && yarn build:client
rm -rf client/build.main
mv client/build client/build.main
git checkout webpack-cleanup-2
yarn build:client
diff -r client/build/ client/build.main/

The diff should exit with no output, showing the webpack output hasn't changed.

For local development, I ran yarn dev, and tested across various pages across localhost:3000 and localhost:5042. I also introduced various typescript and eslint errors into the client code to verify those error/warning messages were shown and failed the build as before.

[caugner]

Changes LGTM, and I compared a local en-US build from this branch with another one from main and saw no differences.