[lldb-dap] When running in server mode settings are shared between debugger instances

If you are using lldb-dap in server mode and set a setting in one instance, those settings would be applied to any new debugger instances created after that point.

For example, if you use `settings set target.run-args 1 2 3` that would be used for all debug sessions after that.

If possible, we should see if we can isolate these settings better.

Start by tracing lldb-dap's server-mode debugger-instance creation and how settings such as target.run-args are stored or inherited. Reproduce the issue by setting target.run-args in one session, then create another session; done means settings from one debugger instance no longer affect later instances.

Written by the indexing model from the issue text.