[Enhancement] (nereids)implement showTrashCommand in nereids

[LiBinfeng-01]

showTrash command is supported in legacy planner but not in nereids(new doris fe planner). you need implement the following showTrash command in nereids:
unsupportedshowTrashStatement
SHOW TRASH (ON backend=STRING_LITERAL)?

[echo-hhj]

I will implement it.

[echo-hhj]

#44352