i#7287 Cache Policies: Added a Release Note on the Refactoring. (DynamoRIO#7395)

Follow up from:
DynamoRIO#7314 (comment)

Added a release note describing the changes in DynamoRIO#7314.

Author: oralmer

api/docs/release.dox

@@ -132,6 +132,12 @@ changes:
  - Added new fields elf_path and elf_path_size to dr_memory_dump_spec_t. When
    dr_create_memory_dump() returns true and elf_path is not NULL, elf_path will be
    written with the path to the memory dump file.
+ - Added a separate cache replacement policy object to `caching_device_t`. `init` now
+   takes an `std::unique_ptr<cache_replacement_policy_t>` that defines the replacement
+   policy. It can be created manually or by using `create_cache_replacement_policy`.
+   Removed the subclasses `cache_lru_t`, `cache_fifo_t`, `tlb_lfu_t`, `tlb_plru_t` that
+   implemented specific cache replacement policies. Added implementations for the
+   matching policies as subclasses of `cache_replacement_policy_t`.
 
 Further non-compatibility-affecting changes include:
  - Changed the types of `block_size`, `total_size`, `num_blocks`, to `int64_t`