Shared artifactory credentials setup.

### Is your feature request related to a problem? Please describe.

I'd like the plugin to setup things such that the we can either use the `jf` function in a Jenkinsfile/job, _and_ the `jf` shell command.

### Describe the solution you'd like to see

We have a number of jobs that use a Makefile, or other build tool, to download assets from Artifactory. In order to make the jenkins build as close to a developer build as possible, we cannot rely on the `jf` function within the Jenkinsfile/job, but instead we want to reply on the `jf` shell command. This allows the Jenkins builds, and developer builds to be as close to repeatable as possible.

### Describe alternatives you've considered

I have a Jenkins shared-library function that does this but it's clunky, may not be very portable.

### Additional context

_No response_

Start by locating the plugin entry points that expose the `jf` Jenkins function and configure credentials, then compare them with how a Jenkinsfile/job invokes the shell `jf` command. Done means both the Jenkins function and shell command can use the configured Artifactory credentials for jobs that run Makefiles or other build tools.

Written by the indexing model from the issue text.