[workspace] Set Jest transformIgnorePatterns to default

[busma13]

This PR makes the following changes:

• In jest.config.base.js explicitly set transformIgnorePatterns to the default (['/node_modules/', '\\.pnp\\.[^\\/]+$']), which will skip running transforms on node-modules or pnp files. We were overriding the default with an empty array. Standard practice is to only transform specific dependencies if there is a need.
• Remove patch for unicorn-magic dependency, as it is no longer being broken by the jest transform.
• Add README to ./patches explaining how to make a patch using patch-package. This also prevents the patches directory from being removed if there are no patches, breaking the docker build.

Ref: #3871, #3874

[sotojn]

Looks good