RFR: 8315716: RISC-V: implement ChaCha20 intrinsic

[Ludovic Henry]

On Mon, 25 Sep 2023 11:47:40 GMT, Hamlin Li <mli at openjdk.org> wrote:

> Only vector version is included in this patch.
> 
> ### Test
> The patch passed the jdk tests found via `find test/jdk/ -iname *ChaCha*`

Marked as reviewed by luhenry (Committer).

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PR Review: https://git.openjdk.org/jdk/pull/15899#pullrequestreview-1646110845