feat: Add priority based memory reclaim framework (#111)

Summary:
Pull Request resolved: #111

* Adds priority base reclaiming to memory reclaim framework. The priority determines which memory pool to reclaim first on the same level. This would help to make reclaim more application logic aware.
* Make join node reclaim priority lower than others. This is because cost of reclaiming (spilling) on join node is high compared to other nodes.

X-link: facebookincubator/velox#11598

Reviewed By: xiaoxmeng

Differential Revision: D66261340

Pulled By: tanjialiang

fbshipit-source-id: c03b2ef25b39dc8771f66321731d5a88da26638e

dwio/nimble/velox/tests/VeloxWriterTests.cpp

@@ -293,7 +293,7 @@ TEST_P(RawStripeSizeFlushPolicyTest, RawStripeSizeFlushPolicy) {
 namespace {
 class MockReclaimer : public velox::memory::MemoryReclaimer {
  public:
-  explicit MockReclaimer() {}
+  explicit MockReclaimer() : velox::memory::MemoryReclaimer(0) {}
   void setEnterArbitrationFunc(std::function<void()>&& func) {
     enterArbitrationFunc_ = func;
   }