Increase default max size for thingHandler thread pool

[lolodomo]

Changed from 5 to 15.

Related to discussion in openhab/openhab-addons#19125

[lolodomo]

The idea would to backport that to OH 5.0 for next patch but not to 4.3.x to avoid impacting small machines with only 1 GB memory. We assume that OH 5 requires a server with more than 1 GB memory and so we can accept a bigger thread pool for bindings.

[lsiepel]

Thanks LGTM

[kaikreuzer]

I am not sure whether this is critical enough to backport to 5.0.x - if someone requires a bigger setting, they can easily change it manually. For all other 5.0 users, it would mean that memory usage is suddenly increased through a "small" patch only.

[lolodomo]

I am now asking myself if 10 would not have been a better compromise?

[lsiepel]

Maybe it is now that the exec also has its own threadpool. There is no magic formula, but smarthome in general, size of installations (requirement) and also the hardware (capacity) has grown over the past few years. An idle thread takes just a very small amount of memory, i wouldn't make a big deal of it.