Refactor auto-generate aeon_acquisition docs

[lochhh]

aeon_acquisition docs are currently generated as .md files using a combination of dotnet and docfx.

This PR:

• standardises the overall structure and looks of aeon_acquisition docs with aeon_mecha by replacing dotnet and docfx with Doxygen (to generate XML docs), Breathe and the Sphinx C# domain (to integrate the XML docs with Sphinx)
• adds external references (e.g. Bonsai, Harp, .NET) in the docs, and closes Broken URL in auto-generated Acquisition API reference #44
• simplifies the env setup with conda env.yml

TODO:

• Update local build instructions in contributing guide

Changes can be previewed here.

[glopesdev]

@lochhh one issue with replacing docfx entirely is we will lose the ability to reference these docs from bonsai itself since we need a xrefmap.yml file.

Also long term we don't necessarily want to document a bonsai library using pure C# docs since bonsai users don't know much about the C# language and it might be misleading for them. We are making standard doc templates for bonsai in docfx and maintaining two stacks of templates will be really hard for us.

Long term I don't really know how best to resolve this yet but I am concerned it will make the docs a bit too different from other packages that people might be lost in how to read them.

Let's discuss next week and I can show some of the existing bonsai package doc pages.