refactor: move hash/maphash linkname bindings to maphash package

Move runtime_rand and runtime_memhash linkname declarations from
runtime/internal/lib/runtime/runtime.go to runtime/internal/lib/hash/maphash/maphash.go
to avoid polluting the runtime package namespace.

Generated with [codeagent](https://github.com/qbox/codeagent)
Co-authored-by: luoliwoshang <luoliwoshang@users.noreply.github.com>

runtime/internal/lib/hash/maphash/maphash.go

@@ -0,0 +1,28 @@
+/*
+ * Copyright (c) 2024 The GoPlus Authors (goplus.org). All rights reserved.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package maphash
+
+import "unsafe"
+
+// llgo:skipall
+type _maphash struct{}
+
+//go:linkname runtime_rand github.com/goplus/llgo/runtime/internal/runtime.fastrand64
+func runtime_rand() uint64
+
+//go:linkname runtime_memhash github.com/goplus/llgo/runtime/internal/runtime.memhash
+func runtime_memhash(p unsafe.Pointer, seed, s uintptr) uintptr

runtime/internal/lib/runtime/runtime.go

@@ -56,18 +56,4 @@ func write(fd uintptr, p unsafe.Pointer, n int32) int32 {
 	return int32(c_write(c.Int(fd), p, c.SizeT(n)))
 }
 
-//go:linkname llgo_fastrand64 github.com/goplus/llgo/runtime/internal/runtime.fastrand64
-func llgo_fastrand64() uint64
-
-//go:linkname llgo_memhash github.com/goplus/llgo/runtime/internal/runtime.memhash
-func llgo_memhash(p unsafe.Pointer, seed, s uintptr) uintptr
-
-func rand() uint64 {
-	return llgo_fastrand64()
-}
-
-func memhash(p unsafe.Pointer, seed, s uintptr) uintptr {
-	return llgo_memhash(p, seed, s)
-}
-
 const heapArenaBytes = 1024 * 1024