fix: update PromPgw option description and refactor MetricPusher initialization

Author: polRk

slo/src/Internal/Cli.cs

@@ -14,7 +14,7 @@ public static class Cli
 
     private static readonly Option<string> PromPgwOption = new(
         "--prom-pgw",
-        "minimum amount of partitions in table") { IsRequired = true };
+        "prometheus push gateway") { IsRequired = true };
 
     private static readonly Option<string> ResourceYdbPath = new(
         new[] { "-t", "--resource-ydb-path" },
@@ -113,4 +113,4 @@ public static async Task<int> Run<T>(SloContext<T> sloContext, string[] args) wh
 
         return await RootCommand.InvokeAsync(args);
     }
-}
+}