[NFC] Use llvm_unreachable instead of lldb::assert

[xbolva00]

Summary

Fixes implicit fall through warnings

[teemperor]

LGTM, thanks!

source/Host/common/Editline.cpp

if (read_count) {
       if (CompleteCharacter(ch, *c))
         return 1;
     } else {
       switch (status) {
       case lldb::eConnectionStatusSuccess: // Success
         break;
 
       case lldb::eConnectionStatusInterrupted:
-        lldbassert(0 && "Interrupts should have been handled above.");
+        llvm_unreachable("Interrupts should have been handled above.");
 
       case lldb::eConnectionStatusError:        // Check GetError() for details
       case lldb::eConnectionStatusTimedOut:     // Request timed out
       case lldb::eConnectionStatusEndOfFile:    // End-of-file encountered
       case lldb::eConnectionStatusNoConnection: // No connection
       case lldb::eConnectionStatusLostConnection: // Lost connection while
                                                   // connected to a valid
                                                   // connection