[foreign-memaccess+abi] RFR: Benchmark Java to/from C string conversions

[Per Minborg]

On Wed, 23 Aug 2023 15:11:39 GMT, Maurizio Cimadamore <mcimadamore at openjdk.org> wrote:

> This PR adds two benchmark to test performance of Java <-> C string conversions.
> The benchmark is not 100% fair, given that JNI has also to transition from Java to native code, but the trend in the benchmark is nevertheless interesting, showing that JNI string conversion scales very poorly with growing string size.
> 
> Thanks to recent optimizations, FFM string conversion is now competitive even for smaller string sizes.

LGTM. Great with a benchmark like this.

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Marked as reviewed by pminborg (Committer).

PR Review: https://git.openjdk.org/panama-foreign/pull/874#pullrequestreview-1598159479