Stop depending on JCenter

[pocmo]

JCenter is going away:
https://jfrog.com/blog/into-the-sunset-bintray-jcenter-gocenter-and-chartcenter/

The official date is May 1st, but the timeline mentions some maintenance beginning April 12th, so let's assume it's gone in April more or less and move on asap.

Some ideas:

• Depend on Maven Central only and see where we are at. A large chunk of our dependencies should be available there. Now there's a high chance more libraries migrate to it. I'm not so sure about older versions of libraries, let's see.
• Everything that isn't available in a reasonable place (we don't want to add random repositories) could be cached by us - either on maven.mozilla.org, or in repos directly too.

This will also affect release branches.

Apps:

• Fenix: Stop depending on JCenter fenix#17819
• Focus: Stop depending on JCenter focus-android#4694
• Reference Browser: Stop depending on JCenter reference-browser#1446

┆Issue is synchronized with this Jira Task

[pocmo]

Here's a nice search query from Christian which looks for JCentral usage in our repositories:
https://github.com/search?q=org%3Amozilla-mobile+jcenter&type=code

[pocmo]

Trying to build AC without jcenter, the first thing I get is:

> Could not resolve all files for configuration ':browser-domains:lintClassPath'.
   > Could not find org.jetbrains.trove4j:trove4j:20160824.
     Searched in the following locations:
       - https://maven.mozilla.org/maven2/org/jetbrains/trove4j/trove4j/20160824/trove4j-20160824.pom
     If the artifact you are trying to retrieve can be found in the repository but without metadata in 'Maven POM' format, you need to adjust the 'metadataSources { ... }' of the repository declaration.
     Required by:
         project :browser-domains > com.android.tools.lint:lint-gradle:27.0.1 > com.android.tools:sdk-common:27.0.1
         project :browser-domains > com.android.tools.lint:lint-gradle:27.0.1 > com.android.tools.external.com-intellij:intellij-core:27.0.1

[pocmo]

This dependency is coming indirectly from the Android Gradle plugin. Unfortunately the latest (stable) version doesn't help.

[owlishDeveloper]

@pocmo were you able to find any sort of workaround for trove4j? I am removing jcenter from geckoview, and for us this is also the only dependency that is still coming from jcenter