Fix yarn watch clean

[matthewwalsh0]

Description

When using yarn watch:clean, we use the --reset-cache argument and also delete the $TMPDIR/react-* directories in an attempt to ensure all source files are compiled from scratch when building.

Despite this, files continue to be cached, and so this PR instead deletes the $TMPDIR/metro-cache directory where the React native cache is now stored.

Steps To Demonstrate Error

1. Provide an expired Infura project ID in .js.env.
2. yarn setup
3. yarn watch:clean
4. yarn start:ios
5. See expected block polling errors.
6. Provide a valid Infura project ID in .js.env.
7. yarn watch:clean
8. yarn start:ios
9. Continue to see expected block polling errors given the compiled Engine.ts including the env is cached.

Checklist

• There is a related GitHub issue
• Tests are included if applicable
• Any added code is fully documented

[github-actions]

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