Add --tablespace option to reindexdb

 Add --tablespace option to reindexdb
 
 This option provides REINDEX (TABLESPACE) for reindexdb, applying the
 tablespace value given by the caller to all the REINDEX queries
 generated.
 
 While on it, this commit adds some tests for REINDEX TABLESPACE, with
 and without CONCURRENTLY, when run on toast indexes and tables.  Such
 operations are not allowed, and toast relation names are not stable
 enough to be part of the main regression test suite (even if using a PL
 function with a TRY/CATCH logic, as CONCURRENTLY could not be tested).
 
 Author: Michael Paquier
 Reviewed-by: Mark Dilger, Daniel Gustafsson
 Discussion: https://postgr.es/m/YDiaDMnzLICqeukl@paquier.xyz