[ARCH-338] Keystore CLI

[connorwstein]

Will add support for sign/encrypt in a follow up, for now just supporting the admin interface. General approach:

• CLI as an importable package so the commands can theoretically be embedded in other cobra CLIs if needed (e.g. if core were to ever move).
• Use json marshaled input/ouput based on the keystore interface existing structs. Easy way to expose batching/API plurality and prevents CLI drift if we add new fields. Support file/stdin input too ("-" for stdin I've seen in kubectl, seems to be relatively standard).
• Env vars for keystore loading parameters - avoids password in shell history and also avoids including them in every CLI command since they are needed for all

[github-actions]

✅ API Diff Results - No breaking changes

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