Partially remove dependency on folly async

Summary:
This change isolates the usage of folly async from Flipper. Is now self-contained in Flipper Folly schedulers.

Users of Flipper can decide not to use the types defined in that header and implement their own.

NOTE: changes are minimal, we are just replacing direct calls to folly event base with a scheduler which simply relays this on to folly.

Reviewed By: fabiomassimo

Differential Revision: D36052198

fbshipit-source-id: 170d64a324a1f1f100224e2622a59cbac3c8b642

iOS/FlipperKit/FlipperClient.mm

@@ -10,9 +10,8 @@
 #import "FlipperClient.h"
 #import <Flipper/FlipperCertificateProvider.h>
 #import <Flipper/FlipperClient.h>
+#import <Flipper/FlipperFollyScopedThreadScheduler.h>
 #import <Flipper/FlipperSocketProvider.h>
-#include <folly/io/async/EventBase.h>
-#include <folly/io/async/ScopedEventBaseThread.h>
 #include <memory>
 #import "FlipperClient+Testing.h"
 #import "FlipperCppWrapperPlugin.h"
@@ -32,8 +31,9 @@ using WrapperPlugin = facebook::flipper::FlipperCppWrapperPlugin;
 
 @implementation FlipperClient {
   facebook::flipper::FlipperClient* _cppClient;
-  folly::ScopedEventBaseThread sonarThread;
-  folly::ScopedEventBaseThread connectionThread;
+  std::unique_ptr<facebook::flipper::Scheduler> sonarScheduler;
+  std::unique_ptr<facebook::flipper::Scheduler> connectionScheduler;
+
   id<FlipperKitCertificateProvider> _certProvider;
 #if !TARGET_OS_OSX && !TARGET_OS_SIMULATOR && !TARGET_OS_MACCATALYST
   FKPortForwardingServer* _secureServer;
@@ -90,6 +90,10 @@ using WrapperPlugin = facebook::flipper::FlipperCppWrapperPlugin;
     deviceName = [[NSHost currentHost] localizedName];
 #endif
 
+    sonarScheduler =
+        std::make_unique<facebook::flipper::FollyScopedThreadScheduler>();
+    connectionScheduler =
+        std::make_unique<facebook::flipper::FollyScopedThreadScheduler>();
     static const std::string UNKNOWN = std::string("unknown");
     try {
       facebook::flipper::FlipperClient::init(
@@ -102,8 +106,8 @@ using WrapperPlugin = facebook::flipper::FlipperCppWrapperPlugin;
                [appId UTF8String] ?: UNKNOWN,
                [privateAppDirectory UTF8String],
            },
-           sonarThread.getEventBase(),
-           connectionThread.getEventBase(),
+           sonarScheduler.get(),
+           connectionScheduler.get(),
            [SKEnvironmentVariables getInsecurePort],
            [SKEnvironmentVariables getSecurePort],
            [SKEnvironmentVariables getAltInsecurePort],