Hide relevant APIs on `Iterable`;
Deprecate `__forEachForJava__` in favor of Java 8 API;
Add `fun messageChainOf(vararg messages: Message): MessageChain`;
Add `fun Array<out Message>.asMessageChain(): MessageChain`;
Add `fun Array<out SingleMessage>.asMessageChain(): MessageChain`;
Add `fun Array<out Message>.flatten(): Sequence<SingleMessage>`;
Add `fun Array<out SingleMessage>.flatten(): Sequence<SingleMessage>`;
Close #312

Deprecate `Message.getOrNull` in favor of `Message.get`;
Add `Message.getOrFail`

1.0.0

Rework `ExternalImage`, introduce `ReusableInput` for multiple attempts when uploading images;
Add `BotConfiguration.fileCacheStrategy`, defaults use cache system from host OS;
Introduce `DeferredReusableInput` for `*.toExternalImage` on JVM.
Deprecate `*.suspendToExternalImage` as no longer need to be suspend.
Open input only when required, close input after uploading files, fix #302

Binary compatibility until 1.2.0.

Migrations:
- `MessagePacket` deprecated in favor of `MessageEvent`
- `MessagePacketBase` deprecated in favor of `MessageEvent`
- `ContactMessage` -> `MessageEvent`
- `FriendMessage` -> `FriendMessageEvent`
- `GroupMessage` -> `GroupMessageEvent`
- `TempMessage` -> `TempMessageEvent`

Fix the error that directly closing the verification code window will block the coroutine.