Switch to slog

[lucacome]

This pull request includes several updates to dependencies, configuration files, and logging mechanisms. The most important changes involve updating Go versions, adding a new linter, and replacing the logging library.

Dependency and configuration updates:

• Updated Go version to 1.23 in .circleci/config.yml and .promu.yml.
• Added sloglint to the list of enabled linters in .golangci.yml.
• Updated github.com/prometheus dependencies to use the new slog logging, which cause the bump to 1.22 in go.mod.

Logging library replacement:

• Replaced github.com/go-kit/log with log/slog across multiple files (main.go, systemd/resolved/resolved.go, systemd/systemd.go).

Code refactoring for logging:

• Updated logging statements in main.go to use the new slog library, including changes in the func main() function.
• Modified logging in systemd/resolved/resolved.go to use slog.Logger and updated error logging.
• Updated logging in systemd/systemd.go to use slog.Logger and updated error logging.

[SuperQ]

Thanks!