Container flag provided but not defined

### What is the issue?

The DockerHub readme documents that `TS_EXTRA_ARGS` are given to `tailscale set`:
https://hub.docker.com/r/tailscale/tailscale#parameters

They're not (at least in current `:latest` v1.92.5), they're given to `tailscale up`, as correctly stated in Tailscale docs:
https://tailscale.com/kb/1282/docker#ts_extra_args

`tailscale up` does not (any longer?) accept args such as `--auto-update`:
https://tailscale.com/kb/1241/tailscale-up

Since the image does not support args other than for `tailscaled` or `tailscale up`, it is not possible to configure such parameters other than by executing `tailscale set` once the container is running.

---

I'd suggest the `TS_EXTRA_ARGS` be given to `tailscale set` as DockerHub claims - alternatively could add a `TS_SET_ARGS`, but I believe it would make the former redundant, as everything that can be configured directly on `up` can also be done with `set`.

### Steps to reproduce

`docker run -e TS_EXTRA_ARGS=--auto-update tailscale/tailscale:v1.92.5` or similar

### Are there any recent changes that introduced the issue?

Yes, but I haven't yet identified - I already had this env var set with an older version; it now fails on startup:
> flag provided but not defined: -auto-update

but possibly the only change is that it now errors about that, and it was always giving it to `tailscale up` which was always doing nothing with it.

### OS

Linux

### OS version

tailscale image

### Tailscale version

1.92.5

### Other software

_No response_

### Bug report

_No response_

Reproduce the startup failure with TS_EXTRA_ARGS=--auto-update using the documented Docker image version, then trace the container's startup handling of tailscale up and tailscale set. Done means the supported argument behavior matches the DockerHub and Tailscale documentation, and the reproduction command no longer fails unexpectedly.

Written by the indexing model from the issue text.