TDBStore: pad record header to whole program size before storing it

Previously, when writing a record header into a TDBStore, we
took the pointer to the record_header_t variable as the input,
but used a program-aligned chunk size which is larger.
As a result, garbage from the stack memory gets written.

This commit fixes that by buffering the record header.

Co-authored-by: Seppo Takalo <[email protected]>

Author: LDong-Arm

storage/kvstore/source/TDBStore.cpp

@@ -847,7 +847,10 @@ int TDBStore::copy_record(uint8_t from_area, uint32_t from_offset, uint32_t to_o
     }
 
     chunk_size = align_up(sizeof(record_header_t), _prog_size);
-    ret = write_area(1 - from_area, to_offset, chunk_size, &header);
+    // The record header takes up whole program units
+    memset(_work_buf, 0, chunk_size);
+    memcpy(_work_buf, &header, sizeof(record_header_t));
+    ret = write_area(1 - from_area, to_offset, chunk_size, _work_buf);
     if (ret) {
         return ret;
     }