Add RM_RdbLoad and RM_RdbSave module API functions (#11852)

Add `RM_RdbLoad()` and `RM_RdbSave()` to load/save RDB files from the module API. 

In our use case, we have our clustering implementation as a module. As part of this
implementation, the module needs to trigger RDB save operation at specific points.
Also, this module delivers RDB files to other nodes (not using Redis' replication).
When a node receives an RDB file, it should be able to load the RDB. Currently,
there is no module API to save/load RDB files. 


This PR adds four new APIs:
```c
RedisModuleRdbStream *RM_RdbStreamCreateFromFile(const char *filename);
void RM_RdbStreamFree(RedisModuleRdbStream *stream);

int RM_RdbLoad(RedisModuleCtx *ctx, RedisModuleRdbStream *stream, int flags);
int RM_RdbSave(RedisModuleCtx *ctx, RedisModuleRdbStream *stream, int flags);
```

The first step is to create a `RedisModuleRdbStream` object. This PR provides a function to
create RedisModuleRdbStream from the filename. (You can load/save RDB with the filename).
In the future, this API can be extended if needed: 
e.g., `RM_RdbStreamCreateFromFd()`, `RM_RdbStreamCreateFromSocket()` to save/load
RDB from an `fd` or a `socket`. 


Usage:
```c
/* Save RDB */
RedisModuleRdbStream *stream = RedisModule_RdbStreamCreateFromFile("example.rdb");
RedisModule_RdbSave(ctx, stream, 0);
RedisModule_RdbStreamFree(stream);

/* Load RDB */
RedisModuleRdbStream *stream = RedisModule_RdbStreamCreateFromFile("example.rdb");
RedisModule_RdbLoad(ctx, stream, 0);
RedisModule_RdbStreamFree(stream);
```

1 files changed, 9 insertions, 0 deletions

diff --git a/src/redismodule.h b/src/redismodule.h
index 13ebc3829..f58da2f49 100644
--- a/src/redismodule.h
+++ b/src/redismodule.h
@@ -881,6 +881,7 @@ typedef struct RedisModuleServerInfoData RedisModuleServerInfoData;
 typedef struct RedisModuleScanCursor RedisModuleScanCursor;
 typedef struct RedisModuleUser RedisModuleUser;
 typedef struct RedisModuleKeyOptCtx RedisModuleKeyOptCtx;
+typedef struct RedisModuleRdbStream RedisModuleRdbStream;
 
 typedef int (*RedisModuleCmdFunc)(RedisModuleCtx *ctx, RedisModuleString **argv, int argc);
 typedef void (*RedisModuleDisconnectFunc)(RedisModuleCtx *ctx, RedisModuleBlockedClient *bc);
@@ -1303,6 +1304,10 @@ REDISMODULE_API int (*RedisModule_RegisterNumericConfig)(RedisModuleCtx *ctx, co
 REDISMODULE_API int (*RedisModule_RegisterStringConfig)(RedisModuleCtx *ctx, const char *name, const char *default_val, unsigned int flags, RedisModuleConfigGetStringFunc getfn, RedisModuleConfigSetStringFunc setfn, RedisModuleConfigApplyFunc applyfn, void *privdata) REDISMODULE_ATTR;
 REDISMODULE_API int (*RedisModule_RegisterEnumConfig)(RedisModuleCtx *ctx, const char *name, int default_val, unsigned int flags, const char **enum_values, const int *int_values, int num_enum_vals, RedisModuleConfigGetEnumFunc getfn, RedisModuleConfigSetEnumFunc setfn, RedisModuleConfigApplyFunc applyfn, void *privdata) REDISMODULE_ATTR;
 REDISMODULE_API int (*RedisModule_LoadConfigs)(RedisModuleCtx *ctx) REDISMODULE_ATTR;
+REDISMODULE_API RedisModuleRdbStream *(*RedisModule_RdbStreamCreateFromFile)(const char *filename) REDISMODULE_ATTR;
+REDISMODULE_API void (*RedisModule_RdbStreamFree)(RedisModuleRdbStream *stream) REDISMODULE_ATTR;
+REDISMODULE_API int (*RedisModule_RdbLoad)(RedisModuleCtx *ctx, RedisModuleRdbStream *stream, int flags) REDISMODULE_ATTR;
+REDISMODULE_API int (*RedisModule_RdbSave)(RedisModuleCtx *ctx, RedisModuleRdbStream *stream, int flags) REDISMODULE_ATTR;
 
 #define RedisModule_IsAOFClient(id) ((id) == UINT64_MAX)
 
@@ -1658,6 +1663,10 @@ static int RedisModule_Init(RedisModuleCtx *ctx, const char *name, int ver, int
     REDISMODULE_GET_API(RegisterStringConfig);
     REDISMODULE_GET_API(RegisterEnumConfig);
     REDISMODULE_GET_API(LoadConfigs);
+    REDISMODULE_GET_API(RdbStreamCreateFromFile);
+    REDISMODULE_GET_API(RdbStreamFree);
+    REDISMODULE_GET_API(RdbLoad);
+    REDISMODULE_GET_API(RdbSave);
 
     if (RedisModule_IsModuleNameBusy && RedisModule_IsModuleNameBusy(name)) return REDISMODULE_ERR;
     RedisModule_SetModuleAttribs(ctx,name,ver,apiver);