Revert "Reland "[lldb-dap] Improving consistency of tests by removing… (#165892)
… concurrency." (#165688)""
This reverts commit 17dbd8690e36f8e514fb47f4418f78420d0fc019.
This was causing timeouts on the premerge runners. Reverting for now
until the timeouts trigger within lit and/or we have a better testing
strategy for this.