ICU-22198 Fix stack buffer overflow.

[kobrineli]

Hi! We've been fuzzing https://github.com/nodejs/node and found stack buffer overflow error in icu in icu4c/source/common/uresbund.cpp. More detailed description of error and how to reproduce is here: nodejs/node#45297

Checklist

• Required: Issue filed: https://unicode-org.atlassian.net/browse/ICU-22198
• 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

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[richgillam]

Good catch.

[kobrineli]

@richgillam
Sorry for disturbing, but the other opened issue in the project, that uses icu as a dependency, is waiting for this pull request to be merged. When will it be possible to merge these changes?

[sffc]

This should be cherry picked to the maintenance branch.