Closes https://github.com/coder/internal/issues/551
We've noticed lots of flakes in `go test -race` tests that use the echo provisioner. I believe the root cause of this to be https://github.com/coder/coder/pull/17012/, where we started mutating the `echo.Responses`. This only caused issues as we previously shared `echo.Responses` across multiple test cases.
This PR is therefore the same as https://github.com/coder/coder/pull/17128, but I believe this is all the cases where an `echo.Responses` is shared between tests - including tests that haven't flaked (yet).
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