Enhancement: Clean up temporary files from codeserver when stopping Development mode

Currently, when stopping development mode, there is no clean up of temporary files in the temporary folder. I recently cleaned up my temporary directory on my dev vm and ended up removing about 7.5GB of data in gwt-codeserver directories. It would be nice, if possible, if the Development mode would clean up the temporary working directories when stopping.

Start by tracing how Development mode handles stopping and where its temporary working directories are created. Confirm which gwt-codeserver files belong to that mode and inspect any existing tests around stop or cleanup behavior. Done means stopping Development mode removes its temporary working directories without affecting unrelated temporary files.

索引モデルが issue の本文から書いたものです。