Allow empty ColList

[Centril]

Description of Changes

Fix the bug found in #1585 by allowing ColLists to be empty, as we actually try to use the type as a possibly-empty list in some places (which is why the tests failed in #1585).

API and ABI breaking changes

None

Expected complexity level and risk

2, some unsafe related code affected, but there's less unsafe code now.

Testing

• Tests were extended to test the empty aspect and the new functionality.
• All the ColList proptests were run in miri.

[kazimuth]

Looks good. Nice to be able to use collect.

I was sketching an implementation of sort as well, since I need it for finding indexes for unique constraints, but it's a little too much added code to do with suggestions.
I'll open a followup PR once this is merged.

[gefjon]

Bump Rust to 1.80.1 as this turned out to be required due to compiler bugs on 1.78.

I would like a more detailed description than this, and would also like to know why bumping to 1.79 is insufficient. I would also strongly prefer the version bump happen in a separate PR, rather than sneaking it in alongside another change.

[Centril]

I would like a more detailed description than this, and would also like to know why bumping to 1.79 is insufficient. I would also strongly prefer the version bump happen in a separate PR, rather than sneaking it in alongside another change.

It was something at some point which caused complaints about #![recursion_limit = "256, 512, ..."] which went away after I bumped the version, but it seems like it works now without a bump, so I removed that from the PR and saved the bump to a different branch.

Rust bump removed from PR.