Update shadow plugin 6.1.0 -> 7.1.1

Version 7.1.1 is absent in jcenter, so additional repository was added
in some modules.

Leave old version in NewMultiplatformIT.kt because of
`This version of Shadow supports Gradle 7.0+ only. Please upgrade.` error.

^KTI-733 Fixed

kotlin-native/tools/kotlin-native-gradle-plugin/build.gradle

@@ -34,7 +34,7 @@ buildscript {
     }
 
     dependencies {
-        classpath 'com.github.jengelman.gradle.plugins:shadow:4.0.4'
+        classpath 'gradle.plugin.com.github.johnrengelman:shadow:7.1.1'
         classpath "org.jetbrains.kotlin:kotlin-native-shared:$konanVersion"
     }
 }