Remove service-glean's hard-dependency on httpurlconnection

We still test with it, so we keep it around.
There is no change for users:

* If they configure an HTTP client it will be used
* If they don't, the default of Glean proper will be used (which is a
  small shim around java.net.HttpURLConnection itself)

Fixes #6660 (at least partly)

components/service/glean/build.gradle

@@ -53,7 +53,6 @@ dependencies {
     implementation project(':support-ktx')
     implementation project(':support-base')
     implementation project(':concept-fetch')
-    implementation project(':lib-fetch-httpurlconnection')
     implementation project(':support-utils')
 
     testImplementation Dependencies.androidx_test_core
@@ -65,6 +64,7 @@ dependencies {
     testImplementation Dependencies.androidx_work_testing
 
     testImplementation project(':support-test')
+    testImplementation project(':lib-fetch-httpurlconnection')
     testImplementation project(':lib-fetch-okhttp')
 
     testImplementation GLEAN_LIBRARY_FORUNITTESTS

components/service/glean/src/main/java/mozilla/components/service/glean/config/Configuration.kt

@@ -4,7 +4,6 @@
 
 package mozilla.components.service.glean.config
 
-import mozilla.components.lib.fetch.httpurlconnection.HttpURLConnectionClient
 import mozilla.components.service.glean.net.ConceptFetchHttpUploader
 import mozilla.telemetry.glean.net.PingUploader
 import mozilla.telemetry.glean.config.Configuration as GleanCoreConfiguration
@@ -23,7 +22,7 @@ data class Configuration @JvmOverloads constructor (
     val serverEndpoint: String = DEFAULT_TELEMETRY_ENDPOINT,
     val channel: String? = null,
     val maxEvents: Int? = null,
-    val httpClient: PingUploader = ConceptFetchHttpUploader(lazy { HttpURLConnectionClient() })
+    val httpClient: PingUploader? = null
 ) {
     // The following is required to support calling our API from Java.
     companion object {
@@ -37,6 +36,12 @@ data class Configuration @JvmOverloads constructor (
      * @return a [mozilla.telemetry.glean.config.Configuration] instance.
      */
     fun toWrappedConfiguration(): GleanCoreConfiguration {
-        return GleanCoreConfiguration(serverEndpoint, channel, maxEvents, httpClient)
+        // Only pass on the HTTP client if one was configured,
+        // otherwise fall back to the default in Glean core.
+        if (httpClient != null) {
+            return GleanCoreConfiguration(serverEndpoint, channel, maxEvents, httpClient)
+        } else {
+            return GleanCoreConfiguration(serverEndpoint, channel, maxEvents)
+        }
     }
 }