[tests] Follow up work for Aspire.Playground.Tests

[radical]

• [ ] Convert the test project to be built on the build machine, and then run on helix similar to workload tests.
• [ ] Test to check that the generated manifest is the same as the on disk. (see https://github.com/dotnet/aspire/pull/5208#issuecomment-2272509638) - https://github.com/dotnet/aspire/issues/4297

Add more playground apps

• [ ] SqlServerEndToEnd (https://github.com/dotnet/aspire/pull/5252)
• [ ] Elasticsearch (https://github.com/dotnet/aspire/pull/5252)
• [ ] PostgresEndToEnd (https://github.com/dotnet/aspire/pull/5252)
• [ ] ParameterEndToEnd (https://github.com/dotnet/aspire/pull/5252)
• [ ] milvus
• [ ] keycloak - https://github.com/dotnet/aspire/pull/5220
• [x] CosmosEndtoEnd - https://github.com/dotnet/aspire/pull/5244 depends on https://github.com/dotnet/aspire/pull/5218

Needs custom test or some work

• [ ] * Bicep (no api service to hit, maybe needs a custom test)
• [ ] withdockerfile - no API to hit. needs a custom test
• [ ] webpubsub - test the webapp?

External resources dependent

• [ ] OpenAIEndToEnd ( Resource could not be provisioned because Azure subscription, location, and resource group information is missing.)
• [ ] Signalr (Resource could not be provisioned because Azure subscription, location, and resource group information is missing)