RFR: 8337832: Optimize datetime toString

[duke]

On Sat, 27 Jul 2024 13:45:11 GMT, Shaojin Wen <duke at openjdk.org> wrote:

> Similar to PR #20321, this improves performance by providing a method that passes in a StringBuilder to avoid unnecessary object allocation.

@wenshao 
Your change (at version 9d7cc54c449d4e12d0eb30c103e8aa3aaf206b6d) is now ready to be sponsored by a Committer.

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PR Comment: https://git.openjdk.org/jdk/pull/20368#issuecomment-2313656091