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.

El issue no menciona archivos, pruebas ni puntos de entrada. Empieza revisando el comportamiento de ejecución de los comandos del ciclo de vida y la especificación existente sobre el paralelismo; aclara si el resultado deseado es la exclusión mutua por grupos o un orden total, y define criterios de aceptación para ambos.

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