Add detailed error message for unsupported casing on Integer

[zliu41]

Error: Unsupported feature: Cannot pattern match on a value of type 'Integer'.

       This usually happens when pattern matching on an integer literal,
       for example:

         f 42 = ...
         f n  = ...

       Plinth does not support pattern matching on 'Integer'. Use equality
       from 'PlutusTx.Prelude' instead, for example:

         import PlutusTx.Prelude ((==))

         f n | n == 42   = ...
             | otherwise = ...

       Note: GHC can generate these unexpectedly, you may need '-fno-strictness', '-fno-specialise', '-fno-spec-constr', '-fno-unbox-strict-fields', or '-fno-unbox-small-strict-fields'.
   |ᴾᴸᴵᴺᵀᴴ
27 |      let y = PlutusTx.divideInteger 42 (f x)

[Unisay]

Nice error message!

Its peculiar that with GHC 9.6 we have 1 golden file change (caseInt) and with 9.12 we have two (caseInt, rangeEnumFromThenTo).

It turns out that:

1. Plugin tries to detect if a symbol has to do with the enumFromTo or other functions from this family:
   https://github.com/IntersectMBO/plutus/blob/master/plutus-tx-plugin/src/PlutusTx/Compiler/Expr.hs#L365
2. This detection stopped working in GHC 9.12 - I suspect they moved symbols like rangeEnumFromThenTo to another namespace, like GHC.Internal.Enum instead of GHC.Enum.

It would be nice if you can fix this regression in this PR since its touching the corresponding test.

[zliu41]

Plugin tries to detect if a symbol has to do with the enumFromTo

This detection stopped working in GHC 9.12

Neither is accurate. enumFromTo is a result of list range syntax [a..b]. I don't think it has anything to do with pattern matching on Integer.

The plugin does try to detect integerEq, which is a result of pattern matching on Integer. But this is fragile, since GHC could easily decide to inline integerEq. This happens in 9.6 as well as 9.12.

[Unisay]

I don't think it has anything to do with pattern matching on Integer.

I think it does: in this PR the golden file rangeEnumFromThenTo.golden.uplc has changed (it contains integer casing error), and it comes from this code:

rangeEnumFromThenTo :: CompiledCode [Integer]
rangeEnumFromThenTo = plinthc [1, 7 .. 50]