genie_python: Alert if something times out

As an instrument scientists I want an alert if an area of code takes too long to execute, so that I am informed if some part of the code has hung, e.g. #5277

### Acceptance criteria

- I can decorate a function with a time value after which I will receive repeated alerts
- I can use a with statement around line of code after which I will receive repeated alerts

### notes

Something like

```
with alert(minutes=5, text="Code stuck", to=555123):
g.cset("freq10", 10)
g.waitfor_block("freq10", 10, 9.5, 10.5)
```

or

```
@alert(minutes=5, text="Code stuck", to=555123)
def set_freq(freq)
g.cset("freq10", freq)
g.waitfor_block("freq10", freq, freq - 0.5, freq + 0.5)
```