[FEATURE] Support RHEL repos #32

Is your feature request related to a problem? Please describe.
I'd like to build base images using RHEL repos. Right now how we do this is build an image outside this tool and use that as the parent for base. That image contains copies of RHEL repo files and the necessary files to access protected Satellite repos.

Describe the solution you'd like
Support either "copyfiles" type operation before packages are installed, so that additional complex repo files can be copied into the build, or support the necessary options to support RHEL repos with entitlement certs.

Describe alternatives you've considered
Right now I build the base image's parent like this:

COPY ./rhel$OS_MAJOR/*.repo /etc/yum.repos.d/

Additional context
This is what repo entry for Satellite host looks like:

[rhel-9-for-x86_64-baseos-rpms]
name = Red Hat Enterprise Linux 9 for x86_64 - BaseOS (RPMs)
baseurl = https://satellite.OMIT/pulp/content/Ohio_Supercomputer_Center/production/OSC_HPC/content/dist/rhel9/9.4/x86_64/baseos/os
enabled = 1
gpgcheck = 1
gpgkey = file:///etc/pki/rpm-gpg/RPM-GPG-KEY-redhat-release
sslverify = 1
sslcacert = /etc/rhsm/ca/katello-server-ca.pem
sslclientkey = /etc/pki/entitlement/479350244350876317-key.pem
sslclientcert = /etc/pki/entitlement/479350244350876317.pem
metadata_expire = 1
enabled_metadata = 1