feat(go): add filter push-down and predicate API for Go binding (#216)

Add complete predicate support to the Go binding, enabling filter
push-down for table scans. This includes:

- C FFI layer: predicate construction functions (equal, not_equal,
  less_than, greater_than, is_null, is_in, etc.), combinators
  (and/or/not), with_filter on ReadBuilder, and fix scan to
  propagate filters via TableScanState
- Go binding: Predicate type, Go-native value types (Date, Time,
  Timestamp, LocalZonedTimestamp, Decimal, Bytes), automatic
  type inference from Go literals (int, string, bool, etc.),
  and ReadBuilder.WithFilter method
- Tests: TestReadWithFilter with shared test helpers

Author: luoyuxia

bindings/c/src/result.rs

@@ -66,6 +66,12 @@ pub struct paimon_result_record_batch_reader {
     pub error: *mut paimon_error,
 }
 
+#[repr(C)]
+pub struct paimon_result_predicate {
+    pub predicate: *mut paimon_predicate,
+    pub error: *mut paimon_error,
+}
+
 #[repr(C)]
 pub struct paimon_result_next_batch {
     pub batch: paimon_arrow_batch,