examples/syntax-test.lus updates

[lorchrob]

Updates to examples/syntax-test.lus.

1. Make sure all the syntax is up to date (e.g., using '(a, b) rather than {a, b} for tuple literals)
2. Remove features we don't support (e.g. various structural assignments and array slices)
3. Add in the new features
   • polymorphism
   • arbitrary-width machine integers
   • unbounded subranges
   • frame blocks
   • if blocks
   • sets and maps
   • history type constructor
   • refinement types
   • any operator
   • transparent and opaque modifiers

Let me know if I forgot anything 🙂

[daniel-larraz]

The new syntax-test.lus file triggers a LustreExpr.Type_mismatch with the current version on develop. Could you please take a look?

In addition, I am missing an example of the nondeterministic choice operator any and the use of the transparent/opaque modifiers.

[lorchrob]

Previous commit addresses the comment about any, transparent, and opaque.

I will take a look at the crash (I suppose the fix should be in a separate PR).