Add support for Expecto theory tests

[Numpsy]

WHAT

Add support for Expecto 'theory' tests

WHY

haf/expecto#445 (comment)

HOW

Added extra cases to the list (to begin with, see other comments)

[Numpsy]

As it stands, this change alone doesn't pick up the theory tests -

The issue seems to be that in visitExpr it picks up the new test cases, but then doesn't add it to the list of tests because the type of the expression is ArrayOrListComputed instead of one of the expected types:

I don't know enough about it to say how it should be changed - e.g. just add a | Case, SynExpr.ArrayOrListComputed to the logic? Add a Theory type to go along side Case and List and look for the Array parameter to that?

edit: or maybe it needs another | SynExpr.App case that matches the 3 parameters to the testTheory call more explicitly?

[Numpsy]

testTheory is a feature of Expecto 10, which only supports .NET 6+, so I updated thise

[TheAngryByrd]

🎸 Thank you!!

[TheAngryByrd]

FYI I fixed the AST stuff in ad2e8ac because yeah that stuff can get gnarly.

[Numpsy]

Ok, VSCode is highlighting all my theory tests in the editor now with Ionide 7.11 :-)