Replace heredocs with static files

[CullenSharp]

Oresat chroot uses heredocs^{1 2} extensively to generate configuration files. It would be better, in my opinion at least, to move this configuration to static files. This allows us to keep the chroot script manageable in size as mission configuration becomes more detailed. As proposed, this changes the workflow.

flowchart LR
1[Copy static files to `etc`] --> 2{Further configuration?}
2 -->|Yes| 3[Shell out to `sed` for templating]
2 -->|No| Done

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This has the potentially greater benefit of simplifying configuration management and deployment.

Footnotes

1. https://en.wikipedia.org/wiki/Here_document ↩

2. https://www.baeldung.com/linux/heredoc-herestring ↩

[CullenSharp]

We can probably also leverage the *.conf files a bit more to insert card and mission specific variables into the build pipeline. The code to do this is found in image-builder/RootStock-NG.sh

. <(m4 -P ${DIR}/configs/${project_config}.conf)

[CullenSharp]

While I'm here, I also suggest splitting the oresat-chroot into card-specific chroot scripts and a single common chroot script.

timeline
t = 0 : oresat-early-chroot
t + 1 : oresat-card-chroot
       : oresat-common-chroot

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