Move kNoExpiration to blob_db.h (#7018)

Summary:
The constant `kNoExpiration` is currently defined in an
internal/implementation header (`blob_log_format.h`); the patch moves it
to the public header `blob_db.h` so it is accessible to users.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/7018

Test Plan: `make check`

Reviewed By: riversand963

Differential Revision: D22191354

Pulled By: ltamasi

fbshipit-source-id: 98c8012a83b999a3f1a30e955ce6bb71ba29dc5c

db/blob/blob_log_format.h

@@ -9,7 +9,6 @@
 
 #ifndef ROCKSDB_LITE
 
-#include <limits>
 #include <memory>
 #include <utility>
 
@@ -23,7 +22,6 @@ namespace blob_db {
 
 constexpr uint32_t kMagicNumber = 2395959;  // 0x00248f37
 constexpr uint32_t kVersion1 = 1;
-constexpr uint64_t kNoExpiration = std::numeric_limits<uint64_t>::max();
 
 using ExpirationRange = std::pair<uint64_t, uint64_t>;
 

utilities/blob_db/blob_db.h

@@ -8,8 +8,10 @@
 #ifndef ROCKSDB_LITE
 
 #include <functional>
+#include <limits>
 #include <string>
 #include <vector>
+
 #include "rocksdb/db.h"
 #include "rocksdb/status.h"
 #include "rocksdb/utilities/stackable_db.h"
@@ -24,6 +26,8 @@ namespace blob_db {
 // The factory needs to be moved to include/rocksdb/utilities to allow
 // users to use blob DB.
 
+constexpr uint64_t kNoExpiration = std::numeric_limits<uint64_t>::max();
+
 struct BlobDBOptions {
   // Name of the directory under the base DB where blobs will be stored. Using
   // a directory where the base DB stores its SST files is not supported.