Improve samples for Healthcare

[maririos]

Now that there is no single document method, there are extra samples that we don't need. We should organize them again and end up having:

• batch convenience async with automatic polling
• batch convenience sync with manual polling
• batch with TextDocumentInput async with automatic polling and with statistics = true
• batch with TextDocumentInput sync with manual polling
• cancellation async
• cancellation sync

[maririos]

Similar to the work done in #17811

Other things to change:

In sample.cs files:

• Sample should also show operation information like CreatedOn, ExpiresOn, etc...
• Sample should also print the relations information
• Sample should check that there were document errors. Example, see here.

sample.md:

• Name needs to change to Sample_AnalyzeHealthcareEntities or Sample8_?.
• Remove section Recognizing healthcare entities in a single document
• Remove the word asynchronously from the description. The idea is that the sample by default shows the sync behavior and at the end there are links for the async behavior
• Description of the content needs to be updated to reflect the new names
• There should be code for the convenience batch and for the TextInputDocument. like here.
• Note how the user shouldn't scroll right in order to see all the content. The sample code needs to be modified so this is reflected. See an example here.

[maririos]

Fixed in #19248