Add description to cache clear config options step

[trvrnrth]

This helps explain the new immediately clear behaviour as well as why you might want to be doing it in the first place.

[zxdavb]

A slight de-tour (because the user did not submit an issue as asked):

In this post, they said:

After clearing the cache 4 of my Evohome zone devices picked up names of the form RAD 01:216136_0x instead of the zone name. Easy to change name and related entity ID’s in the UI of course. Just wondering what the behaviour would be on a new installation via Config Flow.

This makes me wonder if the system is behaving as expected:

• selecting either (or both) options will cause ramses_rf to restart (with/without cached data as permitted) - that is: a new instance of ramses_rf will be created

• if selecting only clear schema, it will reload the packet cache (as permitted) but without any schema packets (0004, 0005 and 000C)

  If it does the latter, it zone names will be missing, but that's OK because restarting ramses_rf will cause discovery to restart...

[zxdavb]

I will test this behaviour later today.

[trvrnrth]

Yeah, I was a bit confused about that as I would expect the initial ramses_rf discovery to pick the zone names up regardless. As a slight correction to the above I believe only 0005 and 000C are removed from the packet cache when clearing the schema (the same as stable did).

[zxdavb]

It will need to be:

if pkt[41:45] not in ["0004", "0005", "000C"]

Reason is: a person will add/remove a zone & be confused it has the old name.

You could argue it should be anything with a zone_idx, but if we immediately discover, it shouldn't be too much of a problem.

Now that I have async send_cmd() calls, with QoS - I'd like to switch from polling to event-driven requests for much of this data.