Cap the number of incrementalMacs populated in an envelope.

Add a remote config `global.maxIncrementalMacsPerEnvelope` (client
fallback of 10) that limits how many attachment pointers in a single
envelope can have their incrementalMac field populated. Each
incrementalMac can be up to 8 KiB, so having too many risks exceeding
the 96 KiB envelope size threshold. Excess attachment pointers have
their incrementalMac and chunkSize fields stripped.

app/src/main/java/org/thoughtcrime/securesms/dependencies/ApplicationDependencyProvider.java

@@ -176,6 +176,7 @@ public class ApplicationDependencyProvider implements AppDependencies.Provider {
                                             Optional.of(new SecurityEventListener(context)),
                                             SignalExecutors.newCachedBoundedExecutor("signal-messages", ThreadUtil.PRIORITY_IMPORTANT_BACKGROUND_THREAD, 1, 16, 30),
                                             RemoteConfig.maxEnvelopeSizeBytes(),
+                                            RemoteConfig.maxIncrementalMacsPerEnvelope(),
                                             RemoteConfig::useMessageSendRestFallback,
                                             RemoteConfig.useBinaryId(),
                                             BuildConfig.USE_STRING_ID);