Improve "Applies to" section for APIs that apply downlevel

[gewarren]

Example: IHttpClientFactory applies to .NET Framework too - see https://apisof.net/catalog/1ded201b-a7dc-5979-02a5-d2c259b08e26.

But the "Applies to" section only shows .NET Platform Extensions 2.0 - 7 and not .NET Framework.

---

Associated WorkItem - 239933

[gewarren]

Here's one idea. We remove the ".NET Platform Extensions moniker" altogether. Instead, any packages that are fed to mdoc should be ingested separately for each of the TFMs in the "lib" folder. Example:

For this package, we see that one of the TFMs it applies to is net462 TFM, which means that the APIs in that assembly can be used in .NET Framework 4.6.2 and later versions. For all APIs in the net462 assembly, we could then display the "applies to" information something like this: