Explicit lifecyle command ordering.

I'm currently working around some of the issues with the `python` feature on bookworm, which ends up involving using `pipx` to install some packages. That's fine.

The problem I'm experiencing is that commands can and are run in parallel, I have multiple packages to install, and `pipx` is (rightfully) rejecting concurrent modifications to parts of the environment it manages.

Obviously, there are multiple workarounds;
- Writing a single shell script to call all the relevant commands
- Concatinating everything together with `&&` or similar.

Both are less than desirable;
- With a shell script, it hides the commands with another level of indirection.
- Concatinating everything together can result in some really long or otherwise hard to parse lines.

So what I'd like is some way to have some way to designate some lifecycle commands as at least mutually exclusive in a "group", or better completely ordered.

Das Issue nennt keine Dateien, Tests oder Einstiegspunkte. Beginne mit der Überprüfung des Ausführungsverhaltens von Lifecycle-Befehlen und der bestehenden Spezifikation für Parallelität; kläre, ob das gewünschte Ergebnis gegenseitiger Ausschluss nach Gruppen oder eine Gesamtordnung ist, und definiere Akzeptanzkriterien für beide.

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