Switch to slog

[lucacome]

This pull request includes several updates to dependencies, configuration files, and logging mechanisms, as well as some minor code refactoring. The most significant changes involve upgrading dependencies, switching from go-kit/log to slog for logging, and updating Go versions.

Dependency and Configuration Updates:

• Updated Go version from 1.22 to 1.23 in .circleci/config.yml and .promu.yml.
• Updated github.com/prometheus dependencies to use the new slog logging, which caused the bump to 1.22 in go.mod.

Logging Changes:

• Replaced go-kit/log with slog for logging in collector.go, pgbouncer_exporter.go, and struct.go.

Linter and Error Handling:

• Updated the linter configuration in .golangci.yml by adding new linters and updating error handling exclusions.
• Removed old error handling exclusions from scripts/errcheck_excludes.txt.

Code Refactoring:

• Refactored variable names in struct.go to fix lint errors.
• Updated function signatures to use *slog.Logger instead of log.Logger in collector.go.

[SuperQ]

LGTM