pg_get_viewdef() and lateral references in COLUMNS of GRAPH_TABLE

pg_get_viewdef() and lateral references in COLUMNS of GRAPH_TABLE

Expressions in GRAPH_TABLE COLUMNS list may have lateral references.
get_rule_expr() requires lateral namespaces to deparse such
references.  get_from_clause_item() does not pass them when processing
the expressions in COLUMNS list causing ERROR "bogus varlevelsup: 0
offset 0".  Fix get_from_clause_item() to pass input deparse_context
containing lateral namespaces to get_rule_expr() instead of the dummy
context.

Author: Satyanarayana Narlapuram <satyanarlapuram@gmail.com>
Reviewed-by: Ashutosh Bapat <ashutosh.bapat.oss@gmail.com>
Discussion: https://www.postgresql.org/message-id/flat/CAHg%2BQDcLVa2iBnggkHxY4itZbXtDMfsYHEjnCUYe9hNbnxDi-w%40mail.gmail.com