Enable explicitApi for mirai-core, add notes for BotFactoryImpl

mirai-core/build.gradle.kts

@@ -34,6 +34,8 @@ afterEvaluate {
 }
 
 kotlin {
+    explicitApi()
+
     if (isAndroidSDKAvailable) {
         apply(from = rootProject.file("gradle/android.gradle"))
         android("android") {

mirai-core/src/commonMain/kotlin/BotFactory.kt

@@ -20,8 +20,12 @@ import net.mamoe.mirai.utils.BotConfiguration
 /**
  * QQ for Android
  */
-@Suppress("INAPPLICABLE_JVM_NAME")
-object BotFactoryImpl : BotFactory {
+@Deprecated(
+    "BotFactoryImpl was accidentally made public, use BotFactory.INSTANCE instead",
+    ReplaceWith("BotFactory", "net.mamoe.mirai.BotFactory"),
+    DeprecationLevel.WARNING,
+)
+public object BotFactoryImpl : BotFactory {
 
     /**
      * 使用指定的 [配置][configuration] 构造 [Bot] 实例

mirai-core/src/commonMain/kotlin/MiraiImpl.kt

@@ -102,6 +102,7 @@ internal open class MiraiImpl : IMirai, LowLevelApiAccessor {
         }
     }
 
+    @Suppress("DEPRECATION")
     override val BotFactory: BotFactory
         get() = BotFactoryImpl