Deprecate --prometheus-cluster-label

The name is misleading. Before this change we had both --prometheus-cluster-label and --prometheus-label which referred to very different things, leading to a bug in the code (to be fixed in the next commit).

We still support -l and have added support for  "--prometheus-cluster-value" which is what `-l` really represents.

README.md

@@ -430,7 +430,7 @@ If your Prometheus monitors multiple clusters we require the label you defined f
 For example, if your cluster has the Prometheus label `cluster: "my-cluster-name"`, then run this command:
 
 ```sh
-krr.py simple --prometheus-label cluster -l my-cluster-name
+krr.py simple --prometheus-cluster-key cluster -l my-cluster-name
 ```
 
 You may also need the `-p` flag to explicitly give Prometheus' URL.

robusta_krr/main.py

@@ -138,15 +138,16 @@ def run_strategy(
                 ),
                 prometheus_cluster_label: Optional[str] = typer.Option(
                     None,
-                    "--prometheus-cluster-label",
+                    "--prometheus-cluster-value",
                     "-l",
-                    help="The label in prometheus for your cluster. (Only relevant for centralized prometheus)",
+                    help="The name of the cluster in Prometheus to scan. e.g. 'gke-prod-1'. Use with `--prometheus-cluster-key`. Only relevant for centralized prometheus.",
                     rich_help_panel="Prometheus Settings",
                 ),
                 prometheus_label: str = typer.Option(
                     None,
+                    "--prometheus-cluster-key",
                     "--prometheus-label",
-                    help="The label in prometheus used to differentiate clusters. (Only relevant for centralized prometheus)",
+                    help="The label in prometheus used to differentiate different clusters (e.g. 'cluster'). Only relevant for centralized prometheus.",
                     rich_help_panel="Prometheus Settings",
                 ),
                 eks_managed_prom: bool = typer.Option(