Adjust SLS files for 15SP7 and systems running higher Python version

[meaksh]

What does this PR change?

In SLE15SP7 there is no more python3-salt package, in favor of new python311-salt.

This PR adjusts the internal Uyuni SLS files that are explicitely mentioning python3-salt package to cover this 15SP7 case.

NOTE: in update-salt.sls and mgr_switch_to_venv_minion.sls we cannot use the pythonversion[1] trick to calculate the target package name, as those SLS bits run also for the Salt Bundle, so the target package calculation can be wrong.

GUI diff

No difference.

• DONE

Documentation

• No documentation needed: only internal and user invisible changes

• DONE

Test coverage

• No tests: already covered

• DONE

Links

Issue(s): https://github.com/SUSE/spacewalk/issues/26711
Port(s):
https://github.com/SUSE/spacewalk/pull/26824
https://github.com/SUSE/spacewalk/pull/26825

• DONE

Changelogs

Make sure the changelogs entries you are adding are compliant with https://github.com/uyuni-project/uyuni/wiki/Contributing#changelogs and https://github.com/uyuni-project/uyuni/wiki/Contributing#uyuni-projectuyuni-repository

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Re-run a test

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• Re-run test "changelog_test"
• Re-run test "backend_unittests_pgsql"
• Re-run test "java_pgsql_tests"
• Re-run test "schema_migration_test_pgsql"
• Re-run test "susemanager_unittests"
• Re-run test "javascript_lint"
• Re-run test "spacecmd_unittests"

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[ycedres]

LGTM.