[Kotlin] Update gradle to 7.4.1 and simplify config files. (#7231)

* [Kotlin] Update gradle to 7.4.1 and simplify config files.

* [Kotlin] Add wrapper-validation-action to Kotlin Linux

* [Kotlin] Remove benchmark actions to reduce CI time

* [Kotlin] Move CI js test to Linux action, to increase Mac action speed

* [Kotlin] Generate gradle wrapper in order to be validate

Gradle wrapper from 3.3 to 4.0 are not verifiable because those files
were dynamically generated by Gradle in a non-reproducible way.

So they are now regenerated and will be checked using gitlab action:
gradle/wrapper-validation-action@v1

kotlin/build.gradle.kts

@@ -1,22 +1,24 @@
 plugins {
-  id("com.diffplug.spotless") version "5.8.2"
+  id("com.diffplug.spotless") version "6.3.0"
 }
 
 group = "com.google.flatbuffers"
 version = "2.0.0-SNAPSHOT"
 
-subprojects {
-
+buildscript {
   repositories {
-    maven { setUrl("https://plugins.gradle.org/m2/") }
+    gradlePluginPortal()
+    google()
     mavenCentral()
   }
+  dependencies {
+    classpath(libs.bundles.plugins)
+  }
 }
 
-buildscript {
+allprojects {
   repositories {
-    maven { setUrl("https://plugins.gradle.org/m2/") }
-    gradlePluginPortal()
+    google()
     mavenCentral()
   }
 }