Deterministic RNG in peer DAS publish block tests

[michaelsproul]

Description

It would be good to make the tests deterministic by using a seeded RNG here:

#5683 (comment)

lighthouse/beacon_node/http_api/src/publish_blocks.rs

Line 128 in ea331a9

data_col_sidecars.shuffle(&mut rand::thread_rng());

[SunnysidedJ]

Hi, I'm a new joinee from Sunnyside Labs and I'd like to work on it. Thanks!

[jimmygchen]

Completed in #7192, thanks @SunnysidedJ !