fix: decrease npm build, bundle size

[TarikGul]

This redirects the build source to reference .npmignore instead of the package.json -> files. I haven't done the exact size comparison, but were looking at a decrease in size by probably 60-70%.

All the tests will now be removed, as well as test-helpers.

[TarikGul]

Just checked the before and after for packages/txwrapper-core, and we are roughly looking at the following, which is a giant improvement.

Before

compressed uncompressed  ratio uncompressed_name
      270425      1630720  83.4% package.tar

After

compressed uncompressed  ratio uncompressed_name
       18439       150528  87.7% package.tar