[Idea] Command to automatically update "cleosrv version update"

flyctl does it, correctly replacing the binary in a fixed location:

```
$ flyctl version update
Update available 0.0.441 -> v0.1.12.
Run "flyctl version update" to upgrade.
/bin/bash -c
Running automatic update [curl -L "https://fly.io/install.sh" | sh]
% Total % Received % Xferd Average Speed Time Time Time Current
Dload Upload Total Spent Left Speed
100 1475 0 1475 0 0 3811 0 --:--:-- --:--:-- --:--:-- 3811
######################################################################## 100,0%
set channel to shell
flyctl was installed successfully to /home/tommy/.fly/bin/flyctl
Run 'flyctl --help' to get started
```

Check how the implement it.

Start at the `cleosrv version update` command and inspect how the existing version command and binary location are handled. Compare the behavior with flyctl's automatic update flow, including replacement of the fixed-location binary. Done means the command can update cleosrv reliably and report the result; no tests or source files are named in the issue.

Written by the indexing model from the issue text.