Summary:
During PG 15 merge the decoding logic for composite types was broken. As a result of this CDC crashed if the record being streamed contained a composite column.

This diff introduces a runtime flag `cdc_disable_sending_composite_values` with default value true. When this flag is set to true, cdc service will skip the decoding logic for composite columns and will send null values instead.

Note: The GH [[ https://github.com/yugabyte/yugabyte-db/issues/25221 | issue ]] tracks the original bug which leads to crash. Once the bug is fixed, `cdc_disable_sending_composite_values` can be set to default false.
Jira: DB-12023

Test Plan:
This revision re-enables composite type tests and validates that we are sending null values
when the flag `cdc_disable_sending_composite_values` is true.

Reviewers: skumar, siddharth.shah

Reviewed By: skumar

Subscribers: ybase, ycdcxcluster

Tags: #jenkins-ready

Differential Revision: https://phorge.dev.yugabyte.com/D40574