KT-34795 Use maven(...) instead of maven { setUrl(...) } for gradle scripts generation

- Use new syntax in tests, but not in actual gradle files
- Reuse public `toKotlinRepositorySnippet` instead of private one
- ^KT-34795 Fixed

idea/testData/gradle/configurator/configureGradleKtsKotlinDevVersion/build.gradle.kts.4.9.after

@@ -9,7 +9,7 @@ dependencies {
     implementation(kotlin("stdlib-jdk8"))
 }
 repositories {
-    maven { setUrl("https://teamcity.jetbrains.com/guestAuth/app/rest/builds/buildType:(id:Kotlin_KotlinPublic_Compiler),number:1.2.60-dev-286,branch:(default:any)/artifacts/content/maven") }
+    maven("https://teamcity.jetbrains.com/guestAuth/app/rest/builds/buildType:(id:Kotlin_KotlinPublic_Compiler),number:1.2.60-dev-286,branch:(default:any)/artifacts/content/maven")
     mavenCentral()
 }
 val compileKotlin: KotlinCompile by tasks

idea/testData/gradle/configurator/configureJsEAPWithBuildGradleKts/build.gradle.kts.after

@@ -6,7 +6,7 @@ version = "1.0-SNAPSHOT"
 
 repositories {
     mavenCentral()
-    maven { setUrl("https://dl.bintray.com/kotlin/kotlin-eap") }
+    maven("https://dl.bintray.com/kotlin/kotlin-eap")
 }
 dependencies {
     implementation(kotlin("stdlib-js"))

idea/testData/gradle/configurator/configureJvmEAPWithBuildGradleKts/build.gradle.kts.after

@@ -10,7 +10,7 @@ version = "1.0-SNAPSHOT"
 
 repositories {
     mavenCentral()
-    maven { setUrl("https://dl.bintray.com/kotlin/kotlin-eap") }
+    maven("https://dl.bintray.com/kotlin/kotlin-eap")
 }
 
 dependencies {