Add in new java API for raw host memory allocation (#17197)

This is the first patch in a series of patches that should make it so that all java host memory allocations go through the DefaultHostMemoryAllocator unless another allocator is explicitly provided. 

This is to make it simpler to track/control host memory usage.

Authors:
  - Robert (Bobby) Evans (https://github.com/revans2)

Approvers:
  - Jason Lowe (https://github.com/jlowe)
  - Alessandro Bellina (https://github.com/abellina)

URL: #17197

java/src/main/java/ai/rapids/cudf/HostMemoryBuffer.java

@@ -1,6 +1,6 @@
 /*
  *
- *  Copyright (c) 2019-2020, NVIDIA CORPORATION.
+ *  Copyright (c) 2019-2024, NVIDIA CORPORATION.
  *
  *  Licensed under the Apache License, Version 2.0 (the "License");
  *  you may not use this file except in compliance with the License.
@@ -155,6 +155,16 @@ public static HostMemoryBuffer allocate(long bytes) {
     return allocate(bytes, defaultPreferPinned);
   }
 
+  /**
+   * Allocate host memory bypassing the default allocator. This is intended to only be used by other allocators.
+   * Pinned memory will not be used for these allocations.
+   * @param bytes size in bytes to allocate
+   * @return the newly created buffer
+   */
+  public static HostMemoryBuffer allocateRaw(long bytes) {
+    return new HostMemoryBuffer(UnsafeMemoryAccessor.allocate(bytes), bytes);
+  }
+
   /**
    * Create a host buffer that is memory-mapped to a file.
    * @param path path to the file to map into host memory