Port `SnapshotVersion` for `Remote` (#1174)

* no-brainer replace FSTSnapshotVersion by SnapshotVersion in `Remote`

* delete `FSTSnapshotVersion` in `Remote`

* fix test

* partially revert RemoteEvent

* Revert "partially revert RemoteEvent"

This reverts commit 67e35bb6c11eaf79608df8d02a60788a40331d0f.

* fix a bug

* fix integration

* address changes

3 files changed, 8 insertions, 4 deletions

diff --git a/Firestore/Example/Tests/Integration/FSTStreamTests.mm b/Firestore/Example/Tests/Integration/FSTStreamTests.mm
index 7e37913..2e5c9b6 100644
--- a/Firestore/Example/Tests/Integration/FSTStreamTests.mm
+++ b/Firestore/Example/Tests/Integration/FSTStreamTests.mm
@@ -29,12 +29,14 @@
 #include "Firestore/core/src/firebase/firestore/auth/empty_credentials_provider.h"
 #include "Firestore/core/src/firebase/firestore/core/database_info.h"
 #include "Firestore/core/src/firebase/firestore/model/database_id.h"
+#include "Firestore/core/src/firebase/firestore/model/snapshot_version.h"
 #include "Firestore/core/src/firebase/firestore/util/string_apple.h"
 
 namespace util = firebase::firestore::util;
 using firebase::firestore::auth::EmptyCredentialsProvider;
 using firebase::firestore::core::DatabaseInfo;
 using firebase::firestore::model::DatabaseId;
+using firebase::firestore::model::SnapshotVersion;
 
 /** Exposes otherwise private methods for testing. */
 @interface FSTStream (Testing)
@@ -101,13 +103,13 @@ using firebase::firestore::model::DatabaseId;
 }
 
 - (void)watchStreamDidChange:(FSTWatchChange *)change
-             snapshotVersion:(FSTSnapshotVersion *)snapshotVersion {
+             snapshotVersion:(const SnapshotVersion &)snapshotVersion {
   [_states addObject:@"watchStreamDidChange"];
   [_expectation fulfill];
   _expectation = nil;
 }
 
-- (void)writeStreamDidReceiveResponseWithVersion:(FSTSnapshotVersion *)commitVersion
+- (void)writeStreamDidReceiveResponseWithVersion:(const SnapshotVersion &)commitVersion
                                  mutationResults:(NSArray<FSTMutationResult *> *)results {
   [_states addObject:@"writeStreamDidReceiveResponseWithVersion"];
   [_expectation fulfill];
diff --git a/Firestore/Example/Tests/Remote/FSTSerializerBetaTests.mm b/Firestore/Example/Tests/Remote/FSTSerializerBetaTests.mm
index bbb3822..437ccd2 100644
--- a/Firestore/Example/Tests/Remote/FSTSerializerBetaTests.mm
+++ b/Firestore/Example/Tests/Remote/FSTSerializerBetaTests.mm
@@ -58,6 +58,7 @@
 
 namespace testutil = firebase::firestore::testutil;
 namespace util = firebase::firestore::util;
+using firebase::Timestamp;
 using firebase::firestore::model::DatabaseId;
 using firebase::firestore::model::FieldMask;
 using firebase::firestore::model::FieldTransform;
@@ -424,8 +425,7 @@ NS_ASSUME_NONNULL_BEGIN
                              precondition:Precondition::UpdateTime(testutil::Version(4))];
   GCFSWrite *proto = [GCFSWrite message];
   proto.update = [self.serializer encodedDocumentWithFields:mutation.value key:mutation.key];
-  proto.currentDocument.updateTime =
-      [self.serializer encodedTimestamp:[[FIRTimestamp alloc] initWithSeconds:0 nanoseconds:4000]];
+  proto.currentDocument.updateTime = [self.serializer encodedTimestamp:Timestamp{0, 4000}];
 
   [self assertRoundTripForMutation:mutation proto:proto];
 }
diff --git a/Firestore/Example/Tests/SpecTests/FSTMockDatastore.h b/Firestore/Example/Tests/SpecTests/FSTMockDatastore.h
index e1ea2fb..4f03a01 100644
--- a/Firestore/Example/Tests/SpecTests/FSTMockDatastore.h
+++ b/Firestore/Example/Tests/SpecTests/FSTMockDatastore.h
@@ -18,6 +18,8 @@
 
 #import "Firestore/Source/Remote/FSTDatastore.h"
 
+@class FSTSnapshotVersion;
+
 NS_ASSUME_NONNULL_BEGIN
 
 @interface FSTMockDatastore : FSTDatastore