Add logs on delete index / create with overwrite option to show quickwit is working during index deletion

Deleting an index with thousands of splits can take a long time (several minutes). You can believe that quickwit is doing nothing, which can be frustrating for a user.

We should a log like "deleting XXXXX splits, this can takes minutes... we can even add a progress bar :). Also, on prompt, we could also warn the user that the operation can last several minutes if there are tens of thousands of splits.

Just adding the current logs on creation with overwrite flag for context:

quickwit-latest index create --index-config ./config/index_config.yaml --config config/indexer_config.yaml --overwrite
2022-10-20T07:31:17.297Z  INFO quickwit: version="0.3.1-nightly" commit="d6b1d30be"
2022-10-20T07:31:17.299Z  INFO quickwit_config::config: Using sniffed advertise address. advertise_address=10.65.50.61 interface_name=ens5
2022-10-20T07:31:17.299Z  INFO quickwit_config::config: Using sniffed advertise address. advertise_address=10.65.50.61 interface_name=ens5
2022-10-20T07:31:17.300Z  INFO quickwit_cli: Loaded Quickwit config. config_uri=file:///home/fmassot/config/indexer_config.yaml config=QuickwitConfig { version: 0, cluster_id: "quickwit-cluster", node_id: "indexer-0", rest_listen_addr: 0.0.0.0:8080, gossip_listen_addr: 0.0.0.0:8080, grpc_listen_addr: 0.0.0.0:8081, gossip_advertise_addr: 10.65.50.61:8080, grpc_advertise_addr: 10.65.50.61:8081, enabled_services: {Indexer, Metastore}, peer_seeds: ["ip-10-65-49-64.eu-west-1.compute.internal:8080"], metastore_uri: Uri { uri: "postgres://quickwit:***redacted***@localhost/poc_quickwit" }, default_index_root_uri: Uri { uri: "s3://cs-external-providers-resources-eu-west-1/quickwit/" }, data_dir_path: "/ephemeral2/quickwit-indexing", indexer_config: IndexerConfig { enable_opentelemetry_otlp_service: false, split_store_max_num_bytes: Byte(150000000000), split_store_max_num_splits: 10000, max_concurrent_split_uploads: 100 }, searcher_config: SearcherConfig { enable_jaeger_service: false, fast_field_cache_capacity: Byte(1000000000), split_footer_cache_capacity: Byte(500000000), max_num_concurrent_split_searches: 100, max_num_concurrent_split_streams: 100 } }
2022-10-20T07:31:17.398Z  INFO sniff_aws_region: quickwit_aws::region: set-aws-region region=EuWest1 from="ec2-instance-metadata-service"
✔ This operation will overwrite the index `quickwit-fts-staging` and delete all its data. Do you want to proceed? · yes

Start at the CLI paths for index deletion and the create --overwrite confirmation, then trace where long-running split deletion is invoked. Review the existing creation logs and prompt behavior. Done means users receive useful progress or duration guidance while deletion is running and a warning about lengthy overwrite operations.