Update libwebrtc version, bump dependencies to latest, refactor to use latest gradle

[sirknightj]

What was changed?

Bumped dependencies, and removed some unused ones.

• com.android.tools.build:gradle:3.5.3 -> 7.3.3
• org.webrtc:google-webrtc:jar:1.0.32006 --> M114
• com.amazonaws:aws-android-sdk-kinesisvideo, com.amazonaws:aws-android-sdk-kinesisvideo-signaling, com.amazonaws:aws-android-sdk-mobile-client, com.amazonaws:aws-android-sdk-auth-userpools, com.amazonaws:aws-android-sdk-kinesisvideo-webrtcstorage 2.68.0 -> 2.73.0
• aws-android-sdk-auth-ui-debug.aar -> com.amazonaws:aws-android-sdk-auth-ui:2.73.0
• org.awaitility:awaitility:3.0.0 -> 4.2.0
• com.google.code.gson:gson:2.8.6 -> 2.8.9
• org.slf4j:slf4j-api:1.7.29 -> x
• com.github.tony19:logback-android:2.0.0 -> x
• commons-codec:commons-codec:1.9 -> x
• org.osgi:org.osgi.framework:1.9.0 -> x
• androidx.appcompat:appcompat:1.1.0 -> 1.6.1
• androidx.constraintlayout:constraintlayout:1.1.3 -> 2.1.4
• com.google.android.material:material:1.0.0 -> 1.9.0
• androidx.multidex:multidex:2.0.1 -> x
• com.dicedmelon.gradle:jacoco-android:0.1.4 -> x

Also, fixed a small UI issue where clicking the triangle back button while on the Channel configuration screen would take you to the empty sign-in activity.

Why was it changed?

• Google is no longer vending out prebuilt binaries of their webrtc library, and have offloaded that responsibility to the consumers. org.webrtc:google-webrtc:jar:1.0.32006 was published on Aug 27, 2020, which is several years old at this point. The last version that Google released contains a dependency with a vulnerability according to https://support.google.com/faqs/answer/12577537?hl=en, which mentions that it has been fixed as of M102. I have built M114 (https://chromiumdash.appspot.com/branches) following https://webrtc.github.io/webrtc-org/native-code/android/ and have included it in the libs folder. The latest webrtc library was not compatible with the version of gradle that was previously used, so that needed bumping. Gradle has changed significantly since the version we were using, so the project structure needed a refactor as well.

Testing

• Tested android as both master and viewer with the JS sample (https://awslabs.github.io/amazon-kinesis-video-streams-webrtc-sdk-js/examples/index.html)
• Verified the sample application is able to connect using the WebRTC ingestion feature in us-west-2.

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[sirknightj]

Added an error message for when libwebrtc is not detected (rather than letting it error out with "class X not found"). Here's what you'll see/run into when building the project without it.