Test coverage - Expand C# SDK test suite

[cloutiertyler]

Definition of Done

• [UNIT] Test to ensure that one off queries work
• [INTEGRATION] Test to ensure that one off queries work
• [INTEGRATION] Test to make sure that you can create a subscription and receive inserts, updates, and deletes
• [INTEGRATION] Test to see that when you submit a query that violates row limit, you receive an appropriate error and not an exception
• [INTEGRATION] Test to change your subscription and ensuring that the new data is applied correctly (all old data is deleted and all new data is inserted)
• [UNIT] Test to ensure that after a message is received on the websocket it takes less than X (reasonable time) to deserialize and populate into the client cache table.

[cloutiertyler]

For integration tests that require testing against SpacetimeDB this repo should assume that SpacetimeDB is running on a standard host and port on the current machine (e.g. localhost:3000)

[rekhoff]

The only fully completed item was:

• [INTEGRATION] Test to ensure that one off queries work - In /sdks/csharp/examples~/regression-tests/client/Program.cs There are several tests that cover this: RemoteQuery, Admins.RemoteQuery, RemoteQuery on View, RemoteQuery on Anonymous View

For the items not-yet checked off:

• [UNIT] one-off queries work
  Not complete, would likely go in sdks/csharp/tests~

• [INTEGRATION] Test to make sure that you can create a subscription and receive inserts, updates, and deletes
  Mostly complete, we have coverage for creating a subscription and for "receive inserts/updates/deletes” via table event hooks, but this doesn't cover explicit callback invocation.

• [INTEGRATION] Test to see that when you submit a query that violates row limit, you receive an appropriate error and not an exception
  Not complete, would likely go in /sdks/csharp/examples~/regression-tests/server/ and /client/

• [INTEGRATION] Test to change your subscription and ensuring that the new data is applied correctly (all old data is deleted and all new data is inserted)
  Not complete. There are some unsubscribe related items in the /regression-tests/client/ and in the tests~/SnapshotTests.cs, but not enough to consider this covered. Would likely go in /sdks/csharp/examples~/regression-tests/server/ and /client/

• [UNIT] Test to ensure that after a message is received on the websocket it takes less than X (reasonable time) to deserialize and populate into the client cache table.
  Not complete. /src/Stats.cs does have some Message related Trackers that could be useful for testing this, and tests~/SnapshotTests.cs does some checkin OnMessageReceived, but not enough to call this covered. I did attempt more coverage on this in a regression test, but we removed it due to the CI runners sometimes causing delays making the test flaky if we didn't use excessively long thresholds for response.