fix: use JUnit 4 imports in test files and add root build config

  - Change test imports from JUnit 5 Jupiter to JUnit 4
  - Add BUILD.bazel with compiler setup initialization
  - Add kotlin.bzl with Kotlin compiler and Spring allopen configuration

Author: kangeunchan

module-a/src/test/kotlin/hs/kr/entrydsm/TestMain.kt

@@ -1,12 +1,11 @@
 package hs.kr.entrydsm.example
 
-import org.junit.jupiter.api.Assertions.assertEquals
-import org.junit.jupiter.api.Test
+import org.junit.Assert.assertEquals
+import org.junit.Test
 
 class ExampleApplicationTest {
     @Test
     fun contextLoads() {
-        // Spring Boot context loading test
         assertEquals(4, 2 + 2)
     }
 }

module-b/src/test/kotlin/hs/kr/entrydsm/TestMain.kt

@@ -1,12 +1,11 @@
 package hs.kr.entrydsm.example
 
-import org.junit.jupiter.api.Assertions.assertEquals
-import org.junit.jupiter.api.Test
+import org.junit.Assert.assertEquals
+import org.junit.Test
 
 class ExampleApplicationTest {
     @Test
     fun contextLoads() {
-        // Spring Boot context loading test
         assertEquals(4, 2 + 2)
     }
 }