pw_kvs: Add flash partition test

Add unit tests for testing flash partition. Put the main test
implementation in to a common file that is used by end tests that
provide the actual partition to test.

Add configuration define PW_FLASH_MAX_FLASH_ALIGNMENT that is
used to size flash write buffers.

Change-Id: Ib3dd2381037d15bd61552184f59769074dece44f
Commit-Queue: David Rogers <>
Reviewed-by: Wyatt Hepler <>
diff --git a/pw_kvs/public/pw_kvs/flash_memory.h b/pw_kvs/public/pw_kvs/flash_memory.h
index ac8f429..46be588 100644
--- a/pw_kvs/public/pw_kvs/flash_memory.h
+++ b/pw_kvs/public/pw_kvs/flash_memory.h
@@ -117,7 +117,7 @@
   const uint32_t sector_size_;
   const uint32_t flash_sector_count_;
-  const uint8_t alignment_;
+  const uint32_t alignment_;
   const uint32_t start_address_;
   const uint32_t start_sector_;
   const std::byte erased_memory_content_;