Remove some global variables in airflow.settings

[jscheffl]

Another small increment to remove global statements for PR #58116

This removes (some - not all) global statements from settings.py where the a lot of state was hold in variables used with global and then a lot of code way relying to access these globals. Is a like a public interface and refactoring would be needed. Attempting to re-sort initialization order to get rid of global.

global is evil.

Note that usage of glocal in ORM engine will be a separate PR

---

Was generative AI tooling used to co-author this PR?

• No (please specify the tool below)

---

• Read the Pull Request Guidelines for more information. Note: commit author/co-author name and email in commits become permanently public when merged.
• For fundamental code changes, an Airflow Improvement Proposal (AIP) is needed.
• When adding dependency, check compliance with the ASF 3rd Party License Policy.
• For significant user-facing changes create newsfragment: {pr_number}.significant.rst or {issue_number}.significant.rst, in airflow-core/newsfragments.

[jscheffl]

Need some other attempt...