[tests] Fix some flaky tests in Aspire.Hosting.Azure.Tests (#5187)

* [tests] ValidateApplicationSamples: use a temporary path for generating the manifest

Other tests also generate and use `postgres.module.bicep` in the tests'
bindir, and these can run in parallel causing them to interfere with
each other.

Issue: #5174

* [tests] ManifestUtils.GetManifestWithBicep: generate in a temporary path

Avoid interfering with other tests by generating the bicep files in
per-test temporyary paths.

`AzureBicepResourceTests.AsAzurePostgresFlexibleServerViaRunMode`
uses `postgres.module.bicep` also, and that file can get overwritten by
other tests like in `AzureBicepResourceTests`.

Issue: #5113

tests/Aspire.Hosting.Tests/Schema/SchemaTests.cs

@@ -195,7 +195,8 @@ public void ValidateApplicationSamples(string testCaseName, Action<IDistributedA
     {
         _ = testCaseName;
 
-        var builder = TestDistributedApplicationBuilder.Create(["--publisher", "manifest", "--output-path", "not-used.json"]);
+        string manifestDir = Directory.CreateTempSubdirectory(testCaseName).FullName;
+        var builder = TestDistributedApplicationBuilder.Create(["--publisher", "manifest", "--output-path", Path.Combine(manifestDir, "not-used.json")]);
         builder.Services.AddKeyedSingleton<IDistributedApplicationPublisher, JsonDocumentManifestPublisher>("manifest");
         configurator(builder);
 

tests/Aspire.Hosting.Tests/Utils/ManifestUtils.cs

@@ -67,19 +67,20 @@ public static async Task<JsonNode[]> GetManifests(IResource[] resources)
 
     public static async Task<(JsonNode ManifestNode, string BicepText)> GetManifestWithBicep(IResource resource)
     {
-        var manifestNode = await GetManifest(resource);
+        string manifestDir = Directory.CreateTempSubdirectory(resource.Name).FullName;
+        var manifestNode = await GetManifest(resource, manifestDir);
 
         if (!manifestNode.AsObject().TryGetPropertyValue("path", out var pathNode))
         {
             throw new ArgumentException("Specified resource does not contain a path property.", nameof(resource));
         }
 
-        if (pathNode?.ToString() is not { } path || !File.Exists(path))
+        if (pathNode?.ToString() is not { } path || !File.Exists(Path.Combine(manifestDir, path)))
         {
             throw new ArgumentException("Path node in resource is null, empty, or does not exist.", nameof(resource));
         }
 
-        var bicepText = await File.ReadAllTextAsync(path);
+        var bicepText = await File.ReadAllTextAsync(Path.Combine(manifestDir, path));
         return (manifestNode, bicepText);
     }
 }