fix: use separate HTTP clients in scale test load generators #21288
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While scale testing, I noticed that our load generators send basically all requests to a single Coderd instance.
e.g.
This is because our scale test commands create all
Runners using the same codersdk Client, which means they share an underlying HTTP client. With HTTP/2 a single TCP session can multiplex many different HTTP requests (including websockets). So, it creates a single TCP connection to a single coderd, and then sends all the requests down the one TCP connections.This PR modifies the
exp scaletestload generator commands to create an independent HTTP client perRunner. This means that each runner will create its own TCP connection. This should help spread the load and make a more realistic test, because in a real deployment, scaled out load will be coming over different TCP connections.