Move class attributes to a more relevant location

[Eric-Arellano]

In class docstring, you can write the Attributes: to enumerate what attributes are available, like MyClass.my_attribute. This is different than the class constructor arguments, like MyClass(my_attribute=1) -- the attributes might not equal the class constructor args.

These attributes are similar to properties from @propery methods, and from class attributes from code values like CLASS_ATTRIBUTE = 1. But one big difference is they are defined in the class docstring directly, like this:

https://github.com/Qiskit/qiskit_sphinx_theme/blob/4606dfde7fcb0d7f65b7cc83f6c56f05aebda9fb/example_docs/api_example/electron.py#L18-L21

We correctly recognize them as <Attribute> components, but we do two confusing things:

1. If there's a type hint, we render the type as **type** so it's bold. It would be better to inline the type so that it's size: str.
2. The attributes show up in the class description, rather than the ## Attributes section where we normally put things. This mirrors Sphinx's behavior, but I think Sphinx is confusing. Ideally we could move these attributes to instead live in the ## Attributes section underneath the class description and constructor.

This is the HTML:

documentation/scripts/lib/api/testdata/qiskit-sphinx-theme/stubs/api_example.Electron.html

Lines 294 to 309 in 7dc37ca

	<dl class="py attribute">
	<dt class="sig sig-object py" id="api_example.Electron.size">
	<span class="sig-name descname"><span class="pre">size</span></span><a class="headerlink" href="#api_example.Electron.size" title="Link to this definition">#</a></dt>
	<dd><p>How big the Electron is.</p>
	<dl class="field-list simple">
	<dt class="field-odd">Type<span class="colon">:</span></dt>
	<dd class="field-odd"><p>str</p>
	</dd>
	</dl>
	</dd></dl>
	<dl class="py attribute">
	<dt class="sig sig-object py" id="api_example.Electron.name">
	<span class="sig-name descname"><span class="pre">name</span></span><a class="headerlink" href="#api_example.Electron.name" title="Link to this definition">#</a></dt>
	<dd><p>What the Electron is called.</p>
	</dd></dl>

This is the MDX from our conversion pipeline (this was before we had the <Attribute> component set up):

documentation/scripts/lib/api/__snapshots__/conversionPipeline.test.ts.snap

Lines 73 to 87 in 7dc37ca

	<span id="api_example.Electron.size" />
	### size
	How big the Electron is.
	**Type**
	str
	<span id="api_example.Electron.name" />
	### name
	What the Electron is called.