[lldb-dap] Refactoring lldb-dap port listening mode to allow multiple connections. (#116392)
This adjusts the lldb-dap listening mode to accept multiple clients.
Each client initializes a new instance of DAP and an associated
`lldb::SBDebugger` instance.
The listening mode is configured with the `--connection` option and
supports listening on a port or a unix socket on supported platforms.
When running in server mode launch and attach performance should
be improved by lldb sharing symbols for core libraries between debug
sessions.