add all exports from a direct child

[weiyuan-jiang]

In GEOSldas, the exports in Catchment or CatchmentCN need to be bubbled up to Land grid comp and to GEOSens grid comp for average. It is inconvenient to add and repeat all exports.

Description

Related Issue

Motivation and Context

How Has This Been Tested?

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)
• Trivial change (affects only documentation or cleanup)

Checklist:

• I have tested this change with a run of GEOSgcm (if non-trivial)
• I have added one of the required labels (0 diff, 0 diff trivial, 0 diff structural, non 0-diff)
• I have updated the CHANGELOG.md accordingly following the style of Keep a Changelog

[mathomp4]

I tested this (along with #1655) with the GCM and it seems zero-diff and good to go.