Summary:
This diff introduces some malloc failure checks that were missing in D40531.
This diff also fixes the incorrect handling of buffer-population failures that can be encountered when building the deploy phase query beyond the query size limit.

Test Plan: Jenkins: all tests, enable connection manager

Reviewers: skumar, mkumar, devansh.saxena

Reviewed By: skumar

Subscribers: yql

Differential Revision: https://phorge.dev.yugabyte.com/D42514