Use --replacepkgs when installing local builds

[jeckersb]

Trying to run tests locally against rawhide was failing, because I
have no local modifications and the same package NEVRA already exists
in the rhcontainerbot/bootc copr repo which is installed previously.

Now if we have the same NEVRA via the local build we'll just
re-install the local version as effectively a no-op instead of
failing.

Signed-off-by: John Eckersberg jeckersb@redhat.com

[gemini-code-assist]

Code Review

This pull request adds the --replacepkgs flag to the rpm installation commands in the Dockerfile and the install-rpm-and-setup script to allow replacing existing packages during local builds. A review comment suggests correcting punctuation and grammar in the newly added documentation block in the installation script.

[cgwalters]

This was also implemented in #2146 which is already in the queue, and this one conflicts.

[jeckersb]

Resurrecting this because it's not totally solved by #2146, I just hit this locally trying to build current main:

[13/14] STEP 6/7: RUN --network=none --mount=type=tmpfs,target=/run --mount=type=tmpfs,target=/tmp     --mount=type=bind,from=packages,src=/,target=/run/packages     rpm -Uvh --oldpackage --nosignature /run/packages/bootc-*.rpm
Verifying...                          ########################################
Preparing...                          ########################################
        package bootc-202604291157.ga360f93080-1.el10.x86_64 is already installed

Rebasing this one and keeping just the change to Containerfile seems enough to fix it on my end.

[jeckersb]

... or not. Apparently the reopen button doesn't actually reopen it, so I'll just make a new PR.

[jeckersb]

➡️ #2180