THRIFT-5775 Kotlin build failed for broken toolchain in docker (#3043)

* THRIFT-5775 Kotlin build failed for broken toolchain in docker

This PR adds JDK 8 to both docker containers to support the kotlin
build.
Kotlin requires toolchain 8 and cant build this without the JDK for that
language level being present.

Also correct readme since docker desktop on Mac also fixes the
permissions with volume sharing automatically.

* Remove gradle toolchains from kotlin and set source/target to java 8

* Manually set the release target for kotlin, remove overwrites from cross-test-client/server

* Set toolchain to 17 on the kotlin lib module
diff --git a/lib/kotlin/cross-test-server/build.gradle.kts b/lib/kotlin/cross-test-server/build.gradle.kts
index eda1ebd..57fef4f 100644
--- a/lib/kotlin/cross-test-server/build.gradle.kts
+++ b/lib/kotlin/cross-test-server/build.gradle.kts
@@ -48,12 +48,6 @@
     testImplementation("org.jetbrains.kotlin:kotlin-test-junit")
 }
 
-kotlin {
-    jvmToolchain {
-        (this as JavaToolchainSpec).languageVersion.set(JavaLanguageVersion.of(8))
-    }
-}
-
 tasks {
     application {
         applicationName = "TestServer"
@@ -68,7 +62,7 @@
 
     task<Exec>("compileThrift") {
         val thriftBin = if (hasProperty("thrift.compiler")) {
-            file(property("thrift.compiler"))
+            file(property("thrift.compiler")!!)
         } else {
             project.rootDir.resolve("../../compiler/cpp/thrift")
         }