Use TLS 1.2 with artifacts API

This commit restricts supported SSL protocols to TLS 1.2 when calling the artifiacts API.
It's possible that a user's machine has older versions of .NET framework installed that default to allow TLS 1.0, causing
the request to fail with:

The request was aborted: Could not create SSL/TLS secure channel.

Author: russcam

src/Elastic.Stack.Artifacts/Resolvers/SnapshotApiResolver.cs

@@ -2,8 +2,10 @@
 using System.Collections.Generic;
 using System.IO;
 using System.Linq;
+using System.Net;
 using System.Net.Http;
 using System.Runtime.InteropServices;
+using System.Security.Authentication;
 using System.Text.Json.Serialization;
 using System.Text.RegularExpressions;
 using System.Threading;
@@ -106,7 +108,11 @@ public static Version LatestReleaseOrSnapshotForMajor(int major)
 				.FirstOrDefault(v => range.IsSatisfied(v.ToString().Replace("-SNAPSHOT", "")));
 		}
 
-		private static HttpClient HttpClient { get; } = new HttpClient() { BaseAddress = new Uri(ArtifactsApiUrl) };
+		private static HttpClient HttpClient { get; } = new HttpClient(new HttpClientHandler
+		{
+			SslProtocols = SslProtocols.Tls12
+		}) { BaseAddress = new Uri(ArtifactsApiUrl) };
+
 		private static string FetchJson(string path)
 		{
 			using (var stream = HttpClient.GetStreamAsync(path).GetAwaiter().GetResult())