Rework 'MOVE ALL' to 'ALTER .. ALL IN TABLESPACE'

As 'ALTER TABLESPACE .. MOVE ALL' really didn't change the tablespace
but instead changed objects inside tablespaces, it made sense to
rework the syntax and supporting functions to operate under the
'ALTER (TABLE|INDEX|MATERIALIZED VIEW)' syntax and to be in
tablecmds.c.

Pointed out by Alvaro, who also suggested the new syntax.

Back-patch to 9.4.