build: use rxjava3

ring-android/app/build.gradle

...c/main/java/cx/ring/account/AccountCreationModelImpl.java

...rc/main/java/cx/ring/account/AccountEditionPresenter.java

.../src/main/java/cx/ring/account/AccountWizardActivity.java

...ain/java/cx/ring/account/HomeAccountCreationFragment.java

...main/java/cx/ring/account/JamiAccountSummaryFragment.java

...rc/main/java/cx/ring/account/ProfileCreationFragment.java

...app/src/main/java/cx/ring/account/RegisterNameDialog.java

...p/src/main/java/cx/ring/adapters/ConversationAdapter.java

...d/app/src/main/java/cx/ring/adapters/RingtoneAdapter.java

.../app/src/main/java/cx/ring/adapters/SmartListAdapter.java

...pp/src/main/java/cx/ring/application/JamiApplication.java

...p/src/main/java/cx/ring/client/AccountSpinnerAdapter.java

.../src/main/java/cx/ring/client/ContactDetailsActivity.java

...in/java/cx/ring/client/ConversationSelectionActivity.java

...ndroid/app/src/main/java/cx/ring/client/HomeActivity.java

...ndroid/app/src/main/java/cx/ring/client/LogsActivity.java

...id/app/src/main/java/cx/ring/client/RingtoneActivity.java

...java/cx/ring/contactrequests/ContactRequestsFragment.java

...java/cx/ring/dependencyinjection/JamiInjectionModule.java