Raise CBOR MaxNestedLevels to 1000 in vespa CLI

[andreer]

Summary

• The vespa CLI prefers CBOR for query responses (`Accept: application/cbor, application/json;q=0.9` in `client/go/internal/cli/cmd/query.go`).
• The CBOR decoder in `client/go/internal/ioutil/ioutil.go` was constructed without setting `MaxNestedLevels`, so it used the fxamacker/cbor default of 32. Responses with deeper nesting (e.g. deep grouping results, large traces) failed to decode with `cbor: exceeded max nested level 32`, surfacing to the user as `failed to decode CBOR response`.
• Set `MaxNestedLevels: 1000`, which should comfortably cover any real Vespa response while staying well under the library's max of 65535.

Test plan

• `go build ./...` in `client/go`
• `go test ./internal/ioutil/... ./internal/cli/cmd/...`
• New `TestCBORToJSONDeepNesting` builds a 100-level nested map and verifies it decodes (would fail under the previous default of 32)