Add MergeUsageAnalyzer to detect legacy merge service usage

- Implemented MergeUsageAnalyzer to flag usage of AdvisoryMergeService and AddMergeModule.
- Created AnalyzerReleases.Shipped.md and AnalyzerReleases.Unshipped.md for release documentation.
- Added tests for MergeUsageAnalyzer to ensure correct diagnostics for various scenarios.
- Updated project files for analyzers and tests to include necessary dependencies and configurations.
- Introduced a sample report structure for scanner output.

src/Scanner/__Tests/StellaOps.Scanner.WebService.Tests/ScansEndpointsTests.cs

@@ -6,6 +6,7 @@ using System.Net;
 using System.Net.Http.Json;
 using System.Linq;
 using System.Text.Json;
+using System.Text.Json.Serialization;
 using System.Threading.Tasks;
 using System.Threading;
 using Microsoft.AspNetCore.Http;
@@ -22,8 +23,8 @@ using StellaOps.Scanner.WebService.Services;
 
 namespace StellaOps.Scanner.WebService.Tests;
 
-public sealed class ScansEndpointsTests
-{
+public sealed class ScansEndpointsTests
+{
     [Fact]
     public async Task SubmitScanReturnsAcceptedAndStatusRetrievable()
     {
@@ -272,7 +273,7 @@ public sealed class ScansEndpointsTests
         var response = await client.GetAsync($"/api/v1/scans/{scanId}/entrytrace");
         Assert.Equal(HttpStatusCode.OK, response.StatusCode);
 
-        var payload = await response.Content.ReadFromJsonAsync<EntryTraceResponse>();
+        var payload = await response.Content.ReadFromJsonAsync<EntryTraceResponse>(SerializerOptions, CancellationToken.None);
         Assert.NotNull(payload);
         Assert.Equal(scanId, payload!.ScanId);
         Assert.Equal("sha256:entrytrace", payload.ImageDigest);
@@ -559,7 +560,7 @@ public sealed class ScansEndpointsTests
         var response = await client.GetAsync($"/api/v1/scans/{scanId}/entrytrace");
         Assert.Equal(HttpStatusCode.OK, response.StatusCode);
 
-        var payload = await response.Content.ReadFromJsonAsync<EntryTraceResponse>();
+        var payload = await response.Content.ReadFromJsonAsync<EntryTraceResponse>(SerializerOptions, CancellationToken.None);
         Assert.NotNull(payload);
         Assert.Equal(storedResult.ScanId, payload!.ScanId);
         Assert.Equal(storedResult.ImageDigest, payload.ImageDigest);
@@ -583,7 +584,10 @@ public sealed class ScansEndpointsTests
         Assert.Equal(HttpStatusCode.NotFound, response.StatusCode);
     }
 
-    private static readonly JsonSerializerOptions SerializerOptions = new(JsonSerializerDefaults.Web);
+    private static readonly JsonSerializerOptions SerializerOptions = new(JsonSerializerDefaults.Web)
+    {
+        Converters = { new JsonStringEnumConverter() }
+    };
 
     private sealed record ProgressEnvelope(
         string ScanId,