Combine first-party Rust builds

[iliana]

Issue #, if available: fixes #291

Description of changes:
Combines all of our first-party Rust builds into a single RPM.

Running cargo install in a loop recompiles every dependency every time because cargo install is not the right tool for this use case. Instead, we're building all the binary targets in workspaces/ at the same time, so we can compile each dependency once.

This lists all the crate names we want to build. Other options included --bins (which does not work with --exclude) or --all --exclude, but since you need to copy the binary in %install anyway it seemed reasonable to list all the crates to build.

This also makes sd_notify the default feature because cargo has strange behavior when trying to enable feature flags while building a workspace, and the discussion appears to be gridlocked between "fix it" and "don't break people", so I kind of just want to steer clear of that entirely.

Timing tests:

Tests performed on an m5.metal, ymmv (but this should be a clear enough improvement to everyone).

Fresh compile (run cargo make clean && cargo make fetch, then time cargo make world):

• current develop: 45m40s
• this branch: 35m1s (10m39s improvement)

Incremental apiserver build (run touch workspaces/api/apiserver/src/bin/apiserver.rs, then time cargo make world):

• current develop: 10m23s
• this branch: 4m27s (5m56s improvement)

Launch tests: An AMI built with these changes boots and joins my cluster.

By submitting this pull request, I confirm that you can use, modify, copy, and redistribute this contribution, under the terms of your choice.

[tjkirch]

Is this related to the other changes in the PR?

[iliana]

I think this failed when I was using --bins, but it's not wrong for us to be using rustls here when we're using it everywhere else.

[sam-aws]

🤘