release-20.2: opt,sql: add EXPLAIN (OPT, MEMO) to show optimizer memo

[exalate-issue-sync]

Mike Lewis (mikeCRL) commented:

PR: cockroachdb/cockroach#67778

From release notes:

Added a new [EXPLAIN flag](../v20.2/explain.html], MEMO, to be used with EXPLAIN (OPT). When the MEMO flag is passed, a representation of the optimizer memo will be printed along with the best plan. The MEMO flag can be used in combination with other flags such as CATALOG and VERBOSE. For example, EXPLAIN (OPT, MEMO, VERBOSE) will print the memo along with verbose output for the best plan. [#67778][#67778) {% comment %}doc{% endcomment %}

Jira Issue: DOC-1852

[mari-crl]

This issue is an accidental duplicate created by automation. The correct issue that is synced to the corresponding Jira issue is #12435.