Move workflow samples under .github

.github/workflows/samples/java-toolchain/build.gradle

@@ -0,0 +1,17 @@
+plugins {
+    id 'java'
+}
+
+java {
+    toolchain {
+        languageVersion = JavaLanguageVersion.of(16)
+    }
+}
+
+repositories {
+    mavenCentral()
+}
+
+dependencies {
+    testImplementation('junit:junit:4.12')
+}