Fix the developer surface for API dependencies. (#536)

We should expose various transitive dependencies to dependants since they're part of the developer surface. Without this users will need to manually redeclare these dependencies to use parts of the library.

Change-Id: I5867e38545ee0c58964717452f28cd64ecd71a40

Author: nwbirnie

buildSrc/src/main/groovy/com.google.api-ads.java-conventions.gradle

@@ -148,15 +148,15 @@ tasks.withType(JavaCompile) {
 }
 
 dependencies {
+  api 'com.google.api:gax'
+  api 'com.google.api:gax-grpc'
+  api 'com.google.protobuf:protobuf-java'
+  api 'io.grpc:grpc-stub'
+  api 'io.grpc:grpc-protobuf'
+  api 'com.google.auth:google-auth-library-oauth2-http'
   implementation platform('com.google.cloud:google-cloud-shared-dependencies:2.4.0')
   implementation 'com.google.guava:guava:30.0-android'
   implementation 'com.google.auto.service:auto-service:1.0-rc2'
-  implementation 'com.google.api:gax'
-  implementation 'com.google.api:gax-grpc'
-  implementation 'com.google.protobuf:protobuf-java'
-  implementation 'io.grpc:grpc-stub'
-  implementation 'io.grpc:grpc-protobuf'
-  implementation 'com.google.auth:google-auth-library-oauth2-http'
   annotationProcessor 'com.google.auto.service:auto-service:1.0-rc2'
   testImplementation 'junit:junit:4.13.1'
 }