perf: Improve locks in SentryScope (#888)

SentryScope contained many locks to self with @synchronized, which are not needed because not the
whole scope is modified in them. Now we only lock the objects that are modified in the
@synchronized block.

Fixes GH-880

CHANGELOG.md

@@ -2,6 +2,8 @@
 
 ## unreleased
 
+- perf: Improve locks in SentryScope #888
+
 ## 6.1.0-alpha.1
 
 - fix: Change maxAttachmentSize from MiB to bytes #891

Sources/Sentry/Public/SentryUser.h

@@ -9,27 +9,27 @@ NS_SWIFT_NAME(User)
 /**
  * Optional: Id of the user
  */
-@property (nonatomic, copy) NSString *userId;
+@property (atomic, copy) NSString *userId;
 
 /**
  * Optional: Email of the user
  */
-@property (nonatomic, copy) NSString *_Nullable email;
+@property (atomic, copy) NSString *_Nullable email;
 
 /**
  * Optional: Username
  */
-@property (nonatomic, copy) NSString *_Nullable username;
+@property (atomic, copy) NSString *_Nullable username;
 
 /**
  * Optional: IP Address
  */
-@property (nonatomic, copy) NSString *_Nullable ipAddress;
+@property (atomic, copy) NSString *_Nullable ipAddress;
 
 /**
  * Optional: Additional data
  */
-@property (nonatomic, strong) NSDictionary<NSString *, id> *_Nullable data;
+@property (atomic, strong) NSDictionary<NSString *, id> *_Nullable data;
 
 /**
  * Initializes a SentryUser with the id