test: improve the code in test-process-hrtime

* use const instead of var
* use assert.strictEqual instead of assert.equal and plain assert
* use arrow functions
* swap assertions arguments to match the standard
* validate the error for assert.throws

PR-URL: https://github.com/nodejs/node/pull/10667


Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Michal Zasso <targos@protonmail.com>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>