[release] 1.18.0 - Persistent storage, ID lists for Data Adapter (#157)

Added an option to provide a custom storage adapter for user-persisted
values `IUserPersistentStorage`. This allows the SDK the persist values
for users in active experiments, in other words, run experiments with
sticky bucketing.

Added support for syncing ID lists from the data adapter.






>Included In This Release
>- 6c7924e kenny-statsig
>   - save list of ids to adapter (#156)
>- a892014 kenny-statsig
>   - EE-205 support ID lists in data adapter (#154)
>- 5cd2c39 kenny-statsig
>   - user persistent storage (#152)
>- 4f830e4 kenny-statsig
>   - replace sleep with wait condition in tests (#153)

statsig_metadata.go

@@ -14,7 +14,7 @@ type statsigMetadata struct {
 func getStatsigMetadata() statsigMetadata {
 	return statsigMetadata{
 		SDKType:         "go-sdk",
-		SDKVersion:      "1.17.0",
+		SDKVersion:      "1.18.0",
 		LanguageVersion: runtime.Version()[2:],
 		SessionID:       SessionID(),
 	}