Tenant UI: display read-only ledgers

[esune]

Currently only ledgers for which an endorser exists are displayed in the Tenant UI, but we want to also display a list of ledgers connected in read-only mode that can be used to receive credentials and compose/validate proofs for issuers rooted on those.

[loneil]

We list these on the Innkeeper Server Configuration by returning the base wallet config from a special Innkeeper endpoint. Probably could just call the tenant's config endpoint and the full ledger list would be in there for a non-innkeeper tenant as well.

[github-actions[bot]]

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