establish consistency for RETURNING column labels

establish consistency for RETURNING column labels

The RETURNING clause now renders columns using the routine as that of the
:class:`.Select` to generate labels, which will include disambiguating
labels, as well as that a SQL function surrounding a named column will be
labeled using the column name itself. This is a more comprehensive change
than a similar one made for the 1.4 series that adjusted the function label
issue only.

includes 1.4's changelog for the backported version which also
fixes an Oracle issue independently of the 2.0 series.

Fixes: #8770
Change-Id: I2ab078a214a778ffe1720dbd864ae4c105a0691d