chore: Use a variable to define port for local registry

[YrrepNoj]

Describe what should be investigated or refactored

Our Makefile uses a local registry to build Zarf packages. Currently, the Makefile is hardcoded to only use port 5000. This doesn't work for all OS's (namely MacOS) as this port is sometimes being used by system processes already.

Make the port that the local registry uses a variable and update the rest of the targets that use the local registry to the variablized port.

Links to any relevant code

leapfrogai/Makefile

Line 35 in 2bf1974

-docker run -d -p 5000:5000 --restart=always --name registry registry:2