test: split test-crypto-dh-hash

test-crypto-dh-hash times out on some platforms. A single test case is
responsible for around 50% of the time to run, so split that test case
into its own file.

PR-URL: https://github.com/nodejs/node/pull/34631


Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: Michaël Zasso <targos@protonmail.com>