Remove the dead-code, in Spider, which is related to the Spider's
HandlerSocket support. The code has been disabled for a long time
and it is unlikely that the code will be enabled.

- rm all files under storage/spider/hs_client/ except hs_compat.h
- rm storage/spider/spd_db_handlersocket.*
- unifdef -UHS_HAS_SQLCOM -UHAVE_HANDLERSOCKET \
  -m storage/spider/spd_* storage/spider/ha_spider.* storage/spider/hs_client/*
- remove relevant files from storage/spider/CMakeLists.txt