Pull out jcsda-emc extensions and repos to put them under spack-stack

[AlexanderRichert-NOAA]

Description

This PR goes along with https://github.com/JCSDA/spack-stack/pull/961. It removes lib/jcsda-emc/, var/spack/repos/jcsda-emc/, and var/spack/repos/jcsda-emc-bundles/.

Issue(s) addressed

Addresses https://github.com/JCSDA/spack-stack/issues/436

Dependencies

none

Impact

n/a

Checklist

• [x] I have performed a self-review of my own code
• [x] I have made corresponding changes to the documentation
• [x] I have run the unit tests before creating the PR

[climbfuji]

This is ready for review, correct?

[AlexanderRichert-NOAA]

Yep, thanks