npm-publish does not support the "prepack" lifecycle script

[brianblakely]

Describe the bug
https://github.com/jfrog/jfrog-cli-core/blob/master/artifactory/utils/npm/pack.go#L16

The above line expects the output of npm pack to be only the filename of the tarball. However, when using the prepack lifecycle script, the output includes information about that script. Because packageFileName is incorrect, the CLI cannot deploy the tarball and throws an error akin to the following:

open /usr/src/app/foo/> @foo/[email protected] prepack /usr/src/app/foo
  > npm run build-lib
  > @foo/[email protected] build-lib /usr/src/app/foo
  > tsc --p tsconfig.lib.json
  foo-bar-9.90.0-alpha.5.tgz: no such file or directory

To Reproduce
Attempt to deploy an npm package via the JFrog CLI npm-publish command with any prepack lifecycle script in package.json.

Expected behavior
The prepack script should run, preparing files for deployment, and the tarball that npm created should be published.

Versions

• JFrog CLI version (if applicable): 1.50.2