tools: make code cache and snapshot deterministic

Use a fixed random seed to ensure that the generated sources are
identical across runs.

The final node binary still reseeds itself on start-up so there should
be no security implications caused by predictable random numbers (e.g.,
`Math.random()`, ASLR, the hash seed, etc.)

Fixes: https://github.com/nodejs/node/issues/29108

PR-URL: https://github.com/nodejs/node/pull/29142


Reviewed-By: Gus Caplan <me@gus.host>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Anna Henningsen <anna@addaleax.net>