feat: go 1.22 and slog migration

[muhlemmer]

This change adds Go 1.22 as a build target and drops support for Go 1.20 and older. The golang.org/x/exp/slog import is migrated to log/slog.

Slog has been part of the Go standard library since Go 1.21. Therefore we are dropping support for older Go versions. This is in line of our support policy of "the latest two Go versions".

Depends on https://github.com/zitadel/logging/pull/21 Closes #549

Definition of Ready

• [x] I am happy with the code
• [x] Short description of the feature/issue is added in the pr description
• [x] PR is linked to the corresponding user story
• [x] Acceptance criteria are met
• [x] All open todos and follow ups are defined in a new ticket and justified
• [x] Deviations from the acceptance criteria and design are agreed with the PO and documented.
• [x] No debug or dead code
• [x] My code has no repetitions
• [x] Critical parts are tested automatically
• [x] Where possible E2E tests are implemented
• [x] Documentation/examples are up-to-date
• [x] All non-functional requirements are met
• [ ] Functionality of the acceptance criteria is checked manually on the dev system.

[github-actions[bot]]

:tada: This PR is included in version 3.13.0 :tada:

The release is available on GitHub release

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