Add 0.10 docs

[coretl]

Initially just an outline of what I will write, in a couple of weeks this PR will have the actual docs in it

[coretl]

@evalott100 please can you make a new branch off this one, then PR back to the docs branch fixing some of the warnings in https://github.com/bluesky/ophyd-async/actions/runs/12911955696/job/36005625932?

Some of them are just missing docstrings, but there are a bunch that say something like:

docstring of ophyd_async.core._signal.set_and_wait_for_value:1: WARNING: py:class reference target not found: ophyd_async.core._signal_backend.SignalDatatypeT

I think this is because importing ophyd_async.core._signal_backend.SignalDatatypeT into ophyd_async.core loses its doc-comment (doc-comment because it is a TypeVar not a class). I have no idea how to get sphinx to recognise that SignalDatatypeT exists and is of a particular type.

I have tried:

• Adding the following to ophyd_async.core.__init__:

"""
.. data:: SignalDatatypeT

    The supported `Signal` datatypes
"""

• Doing the same with .. class:: SignalDatatypeT
• Doing the same but in ophyd_async.core._signal_backend
• Peppering the codebase with from __future__ import annotations

My next steps were going to be:

• Add from __future__ import annotations for everything (don't know if you can do this for the whole module)
• Use autodoc_type_aliases to map ophyd_async.core._signal_backend.SignalDatatypeT to ophyd_async.core.SignalDatatypeT as defined by one of the methods above
• Do some googling