Revert "Move at::{Refcounted,}MapAllocator to c10 (#109881)"

This reverts commit 68a1219f74467a4d2124288f3ab6f8bc471fe4a1.

Reverted https://github.com/pytorch/pytorch/pull/109881 on behalf of https://github.com/kit1980 due to breaking internal builds, undefined symbol: _ZN3c1022RefcountedMapAllocator6decrefEv ([comment](https://github.com/pytorch/pytorch/pull/109881#issuecomment-1761950014))
diff --git a/build_variables.bzl b/build_variables.bzl
index 5f8fcc8..eceb645 100644
--- a/build_variables.bzl
+++ b/build_variables.bzl
@@ -1004,6 +1004,7 @@
     "aten/src/ATen/FunctionalTensorWrapper.cpp",
     "aten/src/ATen/FunctionalizeFallbackKernel.cpp",
     "aten/src/ATen/MemoryOverlap.cpp",
+    "aten/src/ATen/MapAllocator.cpp",
     "aten/src/ATen/NamedTensorUtils.cpp",
     "aten/src/ATen/NestedTensorImpl.cpp",
     "aten/src/ATen/ParallelCommon.cpp",