Update to rand 0.10

[divergentdave]

This PR updates rand and related dependencies. See the documentation for more about this update.

Closes #1386.

[divergentdave]

Version 0.6.0 of rand_distr has been released, so that leaves cargo-vet audits. Here's what's left after skipping rust-lang-owner and WASI-related dependencies.

8 unvetted dependencies:
  chacha20:0.10.0 missing ["safe-to-deploy"]
  cpufeatures:0.3.0 missing ["safe-to-deploy"]
  getrandom:0.4.1 missing ["safe-to-deploy"]
  proc-macro2:1.0.106 missing ["safe-to-deploy"]
  rand:0.10.0 missing ["safe-to-deploy"]
  rand_core:0.10.0 missing ["safe-to-deploy"]
  rand_distr:0.6.0 missing ["safe-to-deploy"]
  syn:2.0.114 missing ["safe-to-deploy"]

recommended audits for safe-to-deploy:
    Command                                    Publisher                         Used By                                   Audit Size
    cargo vet diff syn 2.0.108 2.0.114         dtolnay                           prettyplease, serde_derive, and 3 others  52 files changed, 489 insertions(+), 294 deletions(-)
      NOTE: this project trusts David Tolnay (dtolnay) - consider cargo vet trust syn or cargo vet trust --all dtolnay
    cargo vet diff cpufeatures 0.2.6 0.3.0     github:RustCrypto/utils           chacha20                                  12 files changed, 587 insertions(+), 214 deletions(-)
    cargo vet diff rand_distr 0.5.1 0.6.0      dhardy                            prio                                      36 files changed, 679 insertions(+), 290 deletions(-)
    cargo vet diff getrandom 0.3.3 0.4.1       github:rust-random/getrandom      rand                                      43 files changed, 827 insertions(+), 586 deletions(-)
    cargo vet diff proc-macro2 1.0.95 1.0.106  dtolnay                           syn, quote, prettyplease, and 5 others    20 files changed, 1425 insertions(+), 187 deletions(-)
      NOTE: this project trusts David Tolnay (dtolnay) - consider cargo vet trust proc-macro2 or cargo vet trust --all dtolnay
    cargo vet diff rand 0.9.2 0.10.0           dhardy                            prio, rand_distr, and prio-binaries       36 files changed, 1643 insertions(+), 1328 deletions(-)
    cargo vet diff rand_core 0.9.5 0.10.0      github:rust-random/rand_core      prio, rand, chacha20, and getrandom       19 files changed, 1500 insertions(+), 1686 deletions(-)
    cargo vet inspect chacha20 0.10.0          github:RustCrypto/stream-ciphers  rand                                      4509 lines

estimated audit backlog: 16244 lines

[jcjones]

LGTM!

[tgeoghegan]

Thanks for wading through the audits.