[lldb-dap] Destroy debugger when debug session terminates (#156231)
# Patch
Currently, in Server Mode (i.e. `--connection`), all debuggers are
destroyed when the **lldb-dap process** terminates. This causes logging
and release of resources to be delayed. This can also cause congestion
if multiple debuggers have the same destroy callbacks, which will fight
for the same resources (e.g. web requests) at the same time.
Instead, the debuggers can be destroyed as early as when the **debug
session** terminates. This way, logging and release of release of
resources can happen as soon as possible. Congestion can also be
naturally reduced, because it's unlikely that all debug sessions will
terminate at the same time.
# Tests
See PR #156231.