Description

This refactors AgentEndpoint to use a Cow<Path> instead of a PathBuf so that we can use &'static Path. This avoids an allocation which is a little bit nice, but mainly it's to allow us to make a const one:

AgentEndpoint::Socket(Cow::Borrowed(AgentEndpoint::DEFAULT_UNIX_SOCKET_PATH))

It's a little tricky to make a const &Path because Path::new isn't const, so it uses some unsafe tricks. Note that I ran this by miri locally and it was fine, as I expected.

This UDS path is not necessarily the "best" default because it's only partly true: in practice, we use this as the default agent path if it exists, but if it doesn't, then we use "http://localhost:8126". But it has the distinct advantage of being one that can be defined in const contexts. I plan to use this in another PR to simplify SystemSettings.

Reviewer checklist

• Test coverage seems ok.
• Appropriate labels assigned.