In order to ease the identification of private packages within the monorepo, this adds an `internal-` prefix to all of the current private packages. This makes it immediately clear when reviewing `packages/js` what is and isn't a private package.
* Removed Jetpack Changelogger from test js packages as they follow another approach for handling changelogs.
* Removed composer.json from api-core-tests, e2e-core-tests, e2e-environmnet and e2e-utils as they are no longer needed.
* Removed postinstall script from api-core-tests, e2e-core-tests, e2e-environment and e2e-utils packages, since they will no longer have a composer.json file.
Thanks to our build orchestration tooling, there is
no reason for us to build all of the packages on
`install`. In cases where `prepare` was used to
build before packaging, this changes it to
`prepack` so it will run only under the correct
circumstances.