alter: install space commit/rollback triggers before preparing sql view

sql_compile_view() may fail, in which case the space will never be
deleted from (in case of space creation) or inserted back into (in case
of space drop) the space cache, because commit/rollback triggers, which
are supposed to do the job, are only installed after preparing a view.
Fix this by installing triggers before sql_compile_view().

No need to write a test as without this commit sql/view test will
crash after applying the next commit (the one that introduces space
name cache).

Fixes commit dc358cb0 ("sql: rework VIEW internals").