[Multi-Tenant] Add tenant selection when creating resources in Admin UI

[mkurapov]

Context

As an operator, you should be able to create assets, peers and wallet addresses on behalf of other tenants. We need to reflect this in the UI, and have the tenantId be selectable when creating those resources (via dropdowns).

For non-operator tenants, we can hide the UI elements to select different tenants (since in the backend, the resolvers will use the tenantId from the signature/apollo context).

Todo

• For the create asset page, if you are an operator, we need to provide a dropdown that lists the tenants (with name and id). An operator can then select a particular tenant to create the asset for. This will pass in the tenantId in the createAsset mutation. The mutation input will need to be updated if it hasn't been done so.
• For the create wallet address page, if you are an operator, we need to update the dropdown of assets to provide information about the tenant as well. (alternatively, maybe two dropdowns, where you select the tenant first, then select the asset).
• For the create peers page, if you are an operator, we will need to update the asset dropdown similar to the create wallet address page, such that we can select assets across different tenants.