Fix Go bindings and enable in CI

- Fix all compilation errors in Go bindings
- Add missing type definitions (Pattern, ASTVector, ParamDescrs)
- Fix boolean comparisons to use bool() casts
- Fix Z3_app type casts using unsafe.Pointer
- Fix null symbol handling to use nil
- Fix unused variable in basic_example.go
- Fix CMake test target to run from examples/go directory
- Restore CI steps to build and test Go bindings

Co-authored-by: NikolajBjorner <3085284+NikolajBjorner@users.noreply.github.com>

examples/go/basic_example.go

@@ -82,7 +82,6 @@ func main() {
 	fmt.Println("\nExample 4: Checking unsatisfiability")
 	solver.Reset()
 	a := ctx.MkIntConst("a")
-	one := ctx.MkInt(1, ctx.MkIntSort())
 	
 	// a > 0 ∧ a < 0 (unsatisfiable)
 	solver.Assert(ctx.MkGt(a, zero))