Shared schemes (#738)

* Update .gitignore to not ignored shared settings

`xcshareddata/` should be added to the repo to sync the scheme settings (like running parallel tests or turning on code coverage…)

* Add `bitchat (iOS)` shared scheme

* Parallelized and randomized test execution

* Gather code coverage for `bitchat_iOS` target

.gitignore

@@ -9,9 +9,6 @@ plans/
 CLAUDE.md
 AGENTS.md
 
-## User settings
-xcuserdata/
-
 ## compatibility with Xcode 8 and earlier (ignoring not required starting Xcode 9)
 *.xcscmblueprint
 *.xccheckout
@@ -57,7 +54,8 @@ iOSInjectionProject/
 
 ## Xcode project
 *.xcodeproj/project.xcworkspace/
-*.xcodeproj/xcshareddata/
+## Xcode User settings
+xcuserdata/
 
 ## Python
 __pycache__/