[FEATURE] Nessie integration of Iceberg REST - #7043

Really use a non-default warehouse, configure the warehouse _name_ via the misleadingly named property `CatalogProperties.WAREHOUSE_LOCATION`.

Also eliminate some duplicate code.

and add some unit tests

also remove unused `CatalogServerConfig`

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The Nessie client used from Nessie Catalog is currently a "simple" one. This change lets it use a client that's configured against the actual config+tree resources, which also perform authZ.

Start collecting all base locations in `NessieTableSnapshot`. This change is a start to collect _all_ (base) table locations, to handle cases when a table's (meta)data files are "spread" across multiple base locations. Ideally (and probably usually), each table has only one base location.

* Make `nessie.catalog.default-warehouse` just the optional name of the default warehouse (prevent duplicate configuration).
* Remove `WarehouseConfig.name()` - the name is implicitly defined via the map key of `CatalogConfig.warehouses()`

The handling of secrets is a bit awkward at the moment. We declare "IDs" on the objects, which are to be looked up via the `SecretsProvider`, which is currently just a `Map<String, String>`.

This change changes the behavior: The (default) behavior to lookup via another map is gone.

Secrets are now generally looked up in the following order:
1. If the value is defined on the "per bucket" config, it is used as is.
2. If a secret for the bucket can be resolved, it is used.
3. If the value is defined on the "default" config, it is used as is.
4. If a secret for the "default" config can be resolved, it is used.
5. The secret is assumed to not exist.

The above logic is implemented in the new `SecretsHelper` class. It calls the `SecretProvider` using a collection of keys to look up, which shall return a map with the existing, resolved secrets.

Follow-up, after #7043 is merged to `main`: refactor secrets handlings in "Nessie Core", where/if necessary.

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Co-authored-by: Alexandre Dutra <[email protected]>

- Client `client1` has access to everything.
- Client `client2` has *NO* access to the `sales` namespace.
- Client `client3` has *NO* access to the `eng` namespace.

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Co-authored-by: Alexandre Dutra <[email protected]>

`CONNECT TO` and `USE` working, `SHOW TABLE/VIEW` displays the table/view metadata.

Also adds the `ON initialReference` clause to `CONNECT TO`.