Previously, a query string returned from pg_ivm_get_querydef
did not include column names specified when IMMV was defined
by create_immv. This caused failures in maintenance of MIN/MAX
aggregate views whose columns had alias names.
It is fixed by rewriting the result column name in the parse tree
using the view's tuple descriptor prior to calling pg_get_querydef
for PG15 or higher, or specifying the tuple descriptor to
get_query_def for PG14 or earlier.
In order to re-calculate min/max values for groups where the min
or max value is deleted, we need the view query definition in string
form. However, pg_get_viewdef cannot be used for this purpose because
IMMV's defenition is in pg_ivm_immv but not pg_rewrite. Therefore,
we have to convert query definition in pg_ivm_immv to query
definition string. We can use pg_get_querydef in PG15, but we cannot
in PG14 or earlier, so we use codes in ruleutil.c copied from PG13
or PG14 depending versions.
