Go bindings: extract CGo slice-conversion helpers to eliminate boilerplate

[Copilot]

Reduces repetitive CGo slice-conversion patterns in src/api/go/z3.go by extracting three package-internal helpers, eliminating 13 instances of 4–9 line repeated blocks.

Helpers added

func exprsToASTs(exprs []*Expr) ([]C.Z3_ast, *C.Z3_ast)
func sortsToCSorts(sorts []*Sort) ([]C.Z3_sort, *C.Z3_sort)
func intsToCs(ints []int) ([]C.int, *C.int)

Each returns the backing slice (to keep it alive across the CGo boundary) and a nil-safe pointer to the first element.

Before / After

// Before — repeated in 13 places
cArgs := make([]C.Z3_ast, len(args))
for i, a := range args {
    cArgs[i] = a.ptr
}
var cArgsPtr *C.Z3_ast
if len(cArgs) > 0 {
    cArgsPtr = &cArgs[0]
}
return newExpr(c, C.Z3_mk_atmost(c.ptr, C.uint(len(args)), cArgsPtr, C.uint(k)))

// After
_, cArgsPtr := exprsToASTs(args)
return newExpr(c, C.Z3_mk_atmost(c.ptr, C.uint(len(args)), cArgsPtr, C.uint(k)))

Other simplification

Replaced verbose 5-line if/else C.bool assignments in MkQuantifier and MkQuantifierConst with the direct cast already used elsewhere in the bindings:

forallInt := C.bool(isForall)

Net: −66 lines. No functional changes.