Revert "[lldb] Store SupportFile in FileEntry (NFC)" (#85885)

Reverts llvm/llvm-project#85468 because @slackito reports this broke
stepping in one of their tests [1] and this patch was meant to be NFC.

[1]
d5a277d309 (commitcomment-139991120)

lldb/source/API/SBThread.cpp

@@ -819,7 +819,7 @@ SBError SBThread::StepOverUntil(lldb::SBFrame &sb_frame,
       step_file_spec = sb_file_spec.ref();
     } else {
       if (frame_sc.line_entry.IsValid())
-        step_file_spec = frame_sc.line_entry.GetFile();
+        step_file_spec = frame_sc.line_entry.file;
       else {
         sb_error.SetErrorString("invalid file argument or no file for frame");
         return sb_error;