remove asynchat/asyncore and use asyncio instead

[rerpha]

If we want to use python >=3.12 we need to remove this as it's been deprecated until then and completely removed in 3.12 onwards.

it's currently used by the stream handler, #306 says a bit about this and how we might change it to suit.

acceptance criteria

• asynchat and asyncore are removed from use in favour of asyncio
• our python testing matrix tests against 3.12 and beyond
• the pyproject.toml is updated to use >=3.10 as its python-versions

[Tom-Willemsen]

Short term fix for 3.12 could be to use a shim (https://pypi.org/project/pyasynchat/), but should still do the refactor towards standard asyncio longer term

[anderslindho]

Is there any plan to work on this at ISIS? Asking because we otherwise might want to prioritise doing it at ESS - we have a want for this conversion to remove complicated dependency management.

[Tom-Willemsen]

We don't have any plans to pick this up at ISIS in the immediate future due to short-term capacity constraints, though it remains something we'd like to do in the longer term.

If ESS would like to do this in the short term, we'd be very happy to review a pull-request and provide advice/support where it's useful - even if it's just a draft PR initially proposing an approach. If a PR/issue seems to be ignored (sometimes github notifications can get a bit lost), you can email isisexperimentcontrols@stfc.ac.uk which will get through to our team.

We have quite a few emulators at ISIS, so our preference would be to minimise any changes required on the emulator side (ideally we would keep all changes on the framework side).