tracers: pipeline_snapshot: Misc enhancements

• tracers: pipeline_snapshot: Allow passing dot-dir as a parameter Overriding the default GST_DEBUG_DUMP_DOT_DIR env var

• tracers: pipeline_snapshot: Make it controllable inside apps Exposing properties so that user can configure it when instantiating it

• tracers: pipeline_snapshot: Add a "cleanup-mode" to remove dot files when wanted

• tracers: snapshot: Add an option to add pipeline pts in file names

• tracers: snapshot: Add an option to use folders for each snapshot