Summary:
Decrease size of column when sanitizers are used.
Jira: DB-13666

Test Plan: ./yb_build.sh asan --gtest_filter PgMiniTest.ReadHugeRow -n 4

Reviewers: esheng

Reviewed By: esheng

Subscribers: ybase, yql

Tags: #jenkins-ready

Differential Revision: https://phorge.dev.yugabyte.com/D39450