solved: how to launch a slurm executor from an interactive slurm job

I forget where I saw it in the docs/code where it said not to launch a slurm executor from an `srun` interactive session - which is not quite always possible.

There is a simple workaround - unset `SLURM_*` env vars and then launch and it works just fine.

```
unset $(printenv | grep SLURM | sed -E 's/(.*)=.*/\1/' | xargs)
./my_datatrove_slurm.py
```
Of course, your `srun` session will now be w/o its env vars - which you may or may not care for.

To help others to find the solution, the error is likely to be:

```
srun: error: CPU binding outside of job step allocation, allocated CPUs are: 0x0000000000000FFF80000000000000000000000FFF8000000000.
srun: error: Task launch for StepId=120986.0 failed on node xxx-yyy-11: Unable to satisfy cpu bind request
srun: error: Application launch failed: Unable to satisfy cpu bind request
srun: Job step aborted
```

There is also [this discussion](https://groups.google.com/g/slurm-users/c/mp_JRutKmCc) that proposes to unset just `SLURM_CPU_BIND_*` env vars, so you'd then:

```
unset $(printenv | grep SLURM_CPU_BIND | sed -E 's/(.*)=.*/\1/' | xargs)
./my_datatrove_slurm.py
```

If you want to unset them just for the datatrove launcher use this one-liner syntax
```
SLURM_CPU_BIND= SLURM_CPU_BIND_VERBOSE= SLURM_CPU_BIND_LIST= SLURM_CPU_BIND_TYPE= ./my_datatrove_slurm.py
```
or you could of course unset them inside your script as well, which would make the launching even simpler.

That way all `SLURM_*` env vars will remain intact in your shell environment if you need them for something else.

edit:

I added:

```
import os
# datatrove fails to start slurm jobs from an interactive slurm job,
# so hack to pretend we aren't inside an interactive slurm job by removing SLURM env vars
for key in os.environ.keys():
if key.startswith("SLURM_"):
os.environ.pop(key)
```
on top of my script to make it always work.

No file, test, or entry point is named. Start by locating the Slurm launcher documentation or implementation and verify the interactive-job failure and environment-variable workaround described here. Done means making the workaround discoverable for users launching from an interactive Slurm session.

Written by the indexing model from the issue text.