Add Tiers to Galaxy instances

[hujambo-dunia]

Checklist - before merge:

• data audit on data file .CSV (@hujambo-dunia)
• update to git CODEOWNERS update for data file .CSV changes (Committers)
• approval on data file .CSV (Reviewers)
• approval on Tiers content file .MD (Reviewers)

[mschatz]

I think the tier descriptions need to be expanded. For example, "Tier 2" are national instances (e.g. for all of canada or all of italy) and are quite robust for users in those countries