RFR: 8370822: Improve performance for MemorySegment::fill

[duke]

On Wed, 29 Oct 2025 00:01:57 GMT, Igor Rudenko <duke at openjdk.org> wrote:

> The manual byte-replication expression replaced with the multiplicative expansion trick - a more compact and efficient equivalent.

@hextriclosan 
Your change (at version e3016f39766780efb6705e23b7481aeb311f220f) is now ready to be sponsored by a Committer.

-------------

PR Comment: https://git.openjdk.org/jdk/pull/28031#issuecomment-3479751481