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>

src/api/go/solver.go

@@ -7,7 +7,6 @@ package z3
 import "C"
 import (
 	"runtime"
-	"unsafe"
 )
 
 // Status represents the result of a satisfiability check.