Change maven id to firebase-appdistribution (firebase#3303)

* Change maven id to firebase-appdistribution * Rename firebase-app-distribution directories and gradle files to firebase-appdistribution

Author: rachaprince

firebase-app-distribution-stub/api.txt renamed to firebase-appdistribution-stub/api.txt

@@ -18,7 +18,7 @@ plugins {
 }
 
 firebaseLibrary {
- releaseWith project(':firebase-app-distribution-stub')
+ releaseWith project(':firebase-appdistribution-stub')
  testLab.enabled = true
  publishJavadoc = true
  publishSources = true
@@ -50,7 +50,7 @@ dependencies {
  implementation project(':firebase-components')
  implementation project(':firebase-common:ktx')
  implementation 'androidx.annotation:annotation:1.1.0'
- implementation project(':firebase-app-distribution-stub')
+ implementation project(':firebase-appdistribution-stub')
 
  testImplementation "org.robolectric:robolectric:$robolectricVersion"
  testImplementation 'junit:junit:4.12'