ICU-22801 Try to add LEAKSANITIZER

[FrankYFTang]

Per https://clang.llvm.org/docs/LeakSanitizer.html

Checklist

• Required: Issue filed: https://unicode-org.atlassian.net/browse/ICU-22801
• Required: The PR title must be prefixed with a JIRA Issue number.
• Required: The PR description must include the link to the Jira Issue, for example by completing the URL in the first checklist item
• Required: Each commit message must be prefixed with a JIRA Issue number.
• Issue accepted (done by Technical Committee after discussion)
• Tests included, if applicable
• API docs and/or User Guide docs changed or added, if applicable

[jira-pull-request-webhook]

Hooray! The files in the branch are the same across the force-push. 😃

~ Your Friendly Jira-GitHub PR Checker Bot

[richgillam]

LOKTM.