FY dev

/test @lulf Would you, the tests should pass now that #470 is in. thx

A bit about the status: - it's ready for reviews, and use, actually - when I get conclusion on the discussion places (might tag them with some eye catching emoji...),...

Issues unrelated to random/crypto are now in https://github.com/embassy-rs/trouble/pull/476 . If we merge that in, I can remove them from this PR.

The CI does not really fail - [it says "No space left of device"](https://github.com/embassy-rs/trouble/actions/runs/18651869851/job/53171553648?pr=474#step:5:576). The PR now only includes randomness, and security-related changes (+ ~4 unrelated comments). While it introduces...

NB. CI failing is due to the system not using the modified `.github` actions (in the PR), but the existing `main` ones. I'll come back to this, later... (about 1...