PMM-7 Add tests for custom queries and enhance query execution metrics

[BupycHuk]

No description provided.

[Copilot]

Pull Request Overview

This PR enhances custom query support by refactoring DSN parsing and adding metrics for query execution success/failure. It also updates the Go toolchain version and improves server/database identification.

• Update go.mod file with new Go version and toolchain.
• Refactor DSN parsing by introducing a dedicated parseDSN function and adding parseDatabaseName.
• Add a new metric (pg_exporter_user_queries_executed_total) to track custom query execution results.

Reviewed Changes

Copilot reviewed 7 out of 7 changed files in this pull request and generated 3 comments.

Show a summary per file

File	Description
tools/go.mod	Updated Go version and toolchain details
cmd/postgres_exporter/util.go	Refactored DSN parsing and fingerprint extraction
cmd/postgres_exporter/server.go	Added database name field and corresponding getter
cmd/postgres_exporter/percona_exporter.go	Introduced metric for tracking query execution outcomes
cmd/postgres_exporter/namespace.go	Triggered query execution metric creation for custom queries
cmd/postgres_exporter/main.go	Defined a new constant for database label identification