Update deps

[rukai]

I've patched our bigdecimal version as they are unresponsive to a request for a new version.
It is urgent that we work around this as the new version fixes a flaw in their build.rs that causes most of our dependencies to be rebuilt the second time shotover is compiled (particularly annoying in CI and ec2-cargo)
see: akubera/bigdecimal-rs#114

The other dependency upgrades are straightforward, the new version of nix requires that we set the signals feature to get access to the signals API that we use.

[rukai]

ahh blocked on shotover/tokio-bin-process#24 due to nix being part of tokio-bin-process's api

[rukai]

datastax cpp cassandra driver + TLS tests are segfaulting :/
I cannot reproduce the issue locally via cargo nextest run --all-features cassandra_int_tests::source_tls_and_single_tls

I tracked the issue down to an upgrade of the openssl-sys crate, I think its some cursed linking/UB thing, so I'm just going to pin the crate for now.