Rollup merge of #37589 - raphlinus:fuchsia_random, r=alexcrichton
Rollup merge of #37589 - raphlinus:fuchsia_random, r=alexcrichton

std: Track change to cprng syscall signature (Fuchsia)

The mx_cprng_draw syscall has changed signature to separate the status
and size return values, rather than multiplexing them into a single
value with errors interpreted as a negative value. This patch tracks
that change.

GBGamer/rust,GBGamer/rust,GBGamer/rust,aidancully/rust,GBGamer/rust,aidancully/rust,aidancully/rust,GBGamer/rust,graydon/rust,GBGamer/rust,graydon/rust,graydon/rust,GBGamer/rust,graydon/rust,aidancully/rust,aidancully/rust,graydon/rust,aidancully/rust,graydon/rust,GBGamer/rust