merge v256.{6..11} into musl/stable-v256

• Rebase split-usr MR !4 (closed)

Will need some attention before merging, investigate failing tests.

• 947/1591 systemd:test / test-parse-util broken, as locale is disabled...
• 948/1591 systemd:test / test-time-util
• 986/1591 systemd:libsystemd / test-bus-error
• 1029/1591 systemd:test / test-date (lol '/usr/share/zoneinfo/CEST': No such file or directory)
• 1048/1591 systemd:test / test-errno-util
• 1053/1591 systemd:test / test-fileio
• 1055/1591 systemd:test / test-fs-util
• 1057/1591 systemd:test / test-glob-util
• 1069/1591 systemd:test / test-hostname-util

Path related:

• 1098/1591 systemd:test / test-path-util
• 1590/1591 systemd:core / test-path

Not caring about:

1236/1591 systemd:kernel-install / test-kernel-install
...
1097/1591 systemd:test / test-os-util
...
1349/1591 systemd:example / cc-notify-selfcontained-example-c99
1351/1591 systemd:example / cc-notify-selfcontained-example-c11
1352/1591 systemd:example / cc-notify-selfcontained-example-c90
1353/1591 systemd:example / cc-notify-selfcontained-example-c17
1354/1591 systemd:example / cc-notify-selfcontained-example-c23
1355/1591 systemd:example / cc-notify-selfcontained-example-gnu99
1356/1591 systemd:example / cc-notify-selfcontained-example-gnu90
1357/1591 systemd:example / cc-notify-selfcontained-example-gnu11
1358/1591 systemd:example / cc-notify-selfcontained-example-gnu17
1359/1591 systemd:example / cc-notify-selfcontained-example-gnu23

Known issues:

• 758/1591 systemd:network / test-network: expected HOST_NAME_MAX on musl longer than on glibc. should be safe, when glibc passes this test-suite, as the desired shortening works then.
• 1081/1591 systemd:test / test-locale-util: locale_is_installed("zz_ZZ") == 0 (still) expected musl behaviour