Make the sample presentation of Strict Content use intent

[NSoiffer]

There are currently "sample" renderings. Let's make this use intent.

[davidcarlisle]

Randomly picking a simple example

https://w3c.github.io/mathml/#contm_cn_extended

has

<cn type="rational">22<sep/>7</cn>

rendering as

<mrow><mn>22</mn><mo>/</mo><mn>7</mn></mrow>

My OpenMath/ContentMathML bias wants me to suggest

<mrow intent="rational-number($a,$b)"><mn arg="a">22</mn><mo>/</mo><mn arg="b">7</mn></mrow>

But that's not in the core intent list and I don't think I'd read an element of ℚ differently to the operation of dividing two integers, so I guess either of the core intent entries divide or fraction is suitable (I'd prefer fraction if forced to choose). Or we'd say this is the default intent for an infix / so don't add intent here?

[dginev]

with #426 in mind that example reads closer to:

<mrow intent-isa="rational-number"><mn>22</mn><mo intent="division">/</mo><mn>7</mn></mrow>

the associated concepts from wiki are:

• division
• rational-number

For your "sample presentation" examples you likely don't need to restrict yourself to intent values only from the Core list, as that list is now in the process of being compressed to a point where no realistic text could be annotated using only entries from it. To illustrate, we've discussed that absolute-value is likely to not be in the Core list, but it will be needed for the sample presentation of <abs>, in the 4.3.7.2.1 Examples, namely:

<apply><abs/><ci>x</ci></apply>

<mrow intent="absolute-value($x)">
  <mo>|</mo>
  <mi arg="x">x</mi>
  <mo>|</mo>
</mrow>